Chapter 3: Variable Declarations

Co-authored-by: Dibyendu Majumdar <mobile@majumdar.org.uk> Co-authored-by: Yichen Yan <oraluben@outlook.com> Co-authored-by: Thalia Archibald <thalia@archibald.dev> Co-authored-by: Tamas Hadhazy <helsgithub15@gmail.com> Co-authored-by: Hsiang-Ying Fu <66062782+fuhsnn@users.noreply.github.com> Co-authored-by: XmiliaH <45106915+XmiliaH@users.noreply.github.com> Co-authored-by: Tamás Hadházy <85063808+Hels15@users.noreply.github.com> Co-authored-by: tannal <tannal2409@gmail.com> Co-authored-by: hadha <helsgithub15@gmail.com> Co-authored-by: godalming123 <68993177+godalming123@users.noreply.github.com> Co-authored-by: RobertObkircher <robert.obkircher@gmail.com> Co-authored-by: Jun Kawasaki <jun784@gmail.com>
author: Cliff Click <cliffc@acm.org> 2023-10-01 18:01:54 +0100
committer: Cliff Click <cliffc@acm.org> 2026-10-08 16:52:27 -0700
commit: 2892fa548f7ab10ca146b76b3a608aacccf780d9 (patch)
tree: 4fce21888a1561a72aba5c0ccf9165fa4d8a1ccb
parent: 4968424d5aceefcf5ab6af1c6c0f7d23b9cbfadf (diff)
download: Simple-2892fa548f7ab10ca146b76b3a608aacccf780d9.tar.gz
Simple-2892fa548f7ab10ca146b76b3a608aacccf780d9.zip
27 files changed, 1514 insertions, 16 deletions
diff --git a/README.ja.md b/README.ja.md
index 4c71d15f..141963c6 100644
--- a/README.ja.md
+++ b/README.ja.md
@@ -39,7 +39,7 @@ Simple 言語のスタイルは、C または Java のサブセットに倣っ�
 
 * [第1章](docs/chapter01/README.ja.md)：整数リテラルを返すスクリプト。引数を受け取らず、整数値を1つ返す空の関数。`return` 文。
 * [第2章](docs/chapter02/README.ja.md)：定数を使う加算、減算、乗算、除算などの単純な二項算術演算。ピープホール最適化と単純な定数畳み込み。
-* 第3章：ローカル変数と代入文。右辺での読み取り、SSA、ローカル変数が定数の場合の追加のピープホール最適化。
+* [第3章](docs/chapter03/README.ja.md)：ローカル変数と代入文。右辺での読み取り、SSA、ローカル変数が定数の場合の追加のピープホール最適化。
 * 第4章：`arg` という名前の、定数ではない外部入力変数。定数と `arg` を使う二項演算と比較演算。ゼロ以外の値は真とみなします。代数的簡約によるピープホール最適化。
 * 第5章：`if` 文。制御フローグラフ（CFG）の構築。
 * 第6章：実行されない制御フローに対するピープホール最適化。
diff --git a/README.md b/README.md
index b3bc31d8..08875ed8 100644
--- a/README.md
+++ b/README.md
@@ -42,7 +42,7 @@ The Simple language is styled after a subset of C or Java.
 * [Chapter 1](docs/chapter01/README.md): Script that returns an integer literal, i.e., an empty function that takes no arguments and returns a single integer value. The `return` statement.
 * [Chapter 2](docs/chapter02/README.md): Simple binary arithmetic such as addition, subtraction, multiplication, division
   with constants. Peephole optimization / simple constant folding.
-* Chapter 3: Local variables, and assignment statements. Read on RHS, SSA, more peephole optimization if local is a
+* [Chapter 3](docs/chapter03/README.md): Local variables, and assignment statements. Read on RHS, SSA, more peephole optimization if local is a
   constant.
 * Chapter 4: A non-constant external variable input
   named `arg`.  Binary and Comparison operators involving constants and `arg`.
diff --git a/docs/chapter03/03-grammar.ja.md b/docs/chapter03/03-grammar.ja.md
new file mode 100644
index 00000000..5c79e725
--- /dev/null
+++ b/docs/chapter03/03-grammar.ja.md
@@ -0,0 +1,75 @@
+# 第3章の文法
+
+[English](03-grammar.md) | 日本語
+
+この文書は [原文](03-grammar.md) の日本語訳です。
+
+
+[第3章に戻る](README.ja.md)
+
+```antlrv4
+grammar SimpleLanguage;
+
+program
+    : statement+ EOF
+    ;
+
+statement
+    : returnStatement
+    | declStatement
+    | blockStatment
+    | expressionStatement
+    ;
+
+
+expressionStatement
+    : IDENTIFIER '=' expression ';'
+    ;
+
+blockStatement
+    : '{' statement+ '}'
+    ;
+
+declStatement
+    : 'int' IDENTIFIER '=' expression ';'
+    ;
+
+returnStatement
+    : 'return' expression ';'
+    ;
+
+expression
+    : additiveExpression
+    ;
+
+additiveExpression
+    : multiplicativeExpression (('+' | '-') multiplicativeExpression)*
+    ;
+
+multiplicativeExpression
+    : unaryExpression (('*' | '/') unaryExpression)*
+    ;
+
+unaryExpression
+    : ('-') unaryExpression
+    | primaryExpression
+    ;
+
+primaryExpression
+    : IDENTIFIER
+    | INTEGER_LITERAL
+    | '(' expression ')'
+    ;
+
+INTEGER_LITERAL
+    : [1-9][0-9]*
+    | [0]
+    ;
+
+IDENTIFIER
+    : NON_DIGIT (NON_DIGIT | DIGIT)*
+    ;
+
+NON_DIGIT: [a-zA-Z_];
+DEC_DIGIT: [0-9];
+```
diff --git a/docs/chapter03/03-grammar.md b/docs/chapter03/03-grammar.md
new file mode 100644
index 00000000..3ae8463e
--- /dev/null
+++ b/docs/chapter03/03-grammar.md
@@ -0,0 +1,70 @@
+# Grammar for Chapter 3
+
+English | [日本語](03-grammar.ja.md)
+
+```antlrv4
+grammar SimpleLanguage;
+
+program
+    : statement+ EOF
+    ;
+
+statement
+    : returnStatement
+    | declStatement
+    | blockStatment
+    | expressionStatement
+    ;
+
+
+expressionStatement
+    : IDENTIFIER '=' expression ';'
+    ;
+
+blockStatement
+    : '{' statement+ '}'
+    ;
+
+declStatement
+    : 'int' IDENTIFIER '=' expression ';'
+    ;
+
+returnStatement
+    : 'return' expression ';'
+    ;
+
+expression
+    : additiveExpression
+    ;
+
+additiveExpression
+    : multiplicativeExpression (('+' | '-') multiplicativeExpression)*
+    ;
+
+multiplicativeExpression
+    : unaryExpression (('*' | '/') unaryExpression)*
+    ;
+
+unaryExpression
+    : ('-') unaryExpression
+    | primaryExpression
+    ;
+
+primaryExpression
+    : IDENTIFIER
+    | INTEGER_LITERAL
+    | '(' expression ')'
+    ;
+
+INTEGER_LITERAL
+    : [1-9][0-9]*
+    | [0]
+    ;
+
+IDENTIFIER
+    : NON_DIGIT (NON_DIGIT | DIGIT)*
+    ;
+
+NON_DIGIT: [a-zA-Z_];
+DEC_DIGIT: [0-9];
+```
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new file mode 100644
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+
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+Type not computed
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+Type not computed
+
+[0] → #2  ASSOC</title><circle class="port" cx="60" cy="-3" r="3" fill="#536477"/><text class="slot" x="60" y="-10" text-anchor="middle">0</text></g><g class="node" id="n7" data-id="7" transform="translate(176,134)" style="opacity: 1;"><path class="box" d="M14,0H106Q120,0 120,14V30Q120,44 106,44H14Q0,44 0,30V14Q0,0 14,0Z" fill="#edf3f7"/><text class="label" text-anchor="middle" x="60" y="18"><tspan>+</tspan><tspan class="node-id">  #7</tspan></text><text class="type" text-anchor="middle" y="35" x="60"/><title>#7 +
+Type not computed
+
+[0] → —  DATA
+[1] → #3  DATA
+[2] → #6  DATA</title><circle class="port" cx="30" cy="-3" r="3" fill="white"/><circle class="port" cx="60" cy="-3" r="3" fill="#536477"/><circle class="port" cx="90" cy="-3" r="3" fill="#536477"/><text class="slot" x="30" y="-10" text-anchor="middle">0</text><text class="slot" x="60" y="-10" text-anchor="middle">1</text><text class="slot" x="90" y="-10" text-anchor="middle">2</text></g></g><g class="region-heads" style="opacity: 1;"/><g class="shortcuts" style="opacity: 1;"/><g class="peep-ghosts" pointer-events="none"/></g></svg>
diff --git a/docs/chapter03/03-graph2.gv b/docs/chapter03/03-graph2.gv
new file mode 100644
index 00000000..cafa7f25
--- /dev/null
+++ b/docs/chapter03/03-graph2.gv
@@ -0,0 +1,35 @@
+digraph chapter03 {
+/*
+int a=1; int b=2; int c=0; { int b=3; c=a+b;  } return c;
+*/
+	rankdir=BT;
+	ordering="in";
+	concentrate="true";
+	subgraph cluster_Nodes {
+		Start2 [ shape=box style=filled fillcolor=yellow label="Start" ];
+		Con_3 [ label="#1" ];
+		Con_4 [ label="#2" ];
+		Con_6 [ label="#3" ];
+		Add7 [ label="+" ];
+		Return8 [ shape=box style=filled fillcolor=yellow label="Return" ];
+	}
+	node [shape=plaintext];
+	subgraph cluster_Scope1_0 {
+		Scope1_0 [label=<
+			<TABLE BORDER="0" CELLBORDER="1" CELLSPACING="0">
+			<TR><TD BGCOLOR="cyan">0</TD><TD PORT="Scope1_0_a">a</TD><TD PORT="Scope1_0_b">b</TD><TD PORT="Scope1_0_c">c</TD></TR>
+			</TABLE>>];
+	}
+	edge [ fontname=Helvetica, fontsize=8 ];
+	Con_3 -> Start2[taillabel=0 style=dotted];
+	Con_4 -> Start2[taillabel=0 style=dotted];
+	Con_6 -> Start2[taillabel=0 style=dotted];
+	Add7 -> Con_3[taillabel=1];
+	Add7 -> Con_6[taillabel=2];
+	Return8 -> Start2[taillabel=0 color=red];
+	Return8 -> Add7[taillabel=1];
+	edge [style=dashed color=cornflowerblue];
+	Scope1_0:"Scope1_0_a" -> Con_3;
+	Scope1_0:"Scope1_0_b" -> Con_4;
+	Scope1_0:"Scope1_0_c" -> Add7;
+}
diff --git a/docs/chapter03/03-graph2.json b/docs/chapter03/03-graph2.json
new file mode 100644
index 00000000..80397161
--- /dev/null
+++ b/docs/chapter03/03-graph2.json
@@ -0,0 +1,18 @@
+{
+  "ver": 1,
+  "comp": "chapter03/docs/03-graph2.svg",
+  "step": 1,
+  "roots": [],
+  "scope": 0,
+  "nodes": [
+    {"id": 1, "label": "Scope", "type": null, "kind": "SCOPE", "edges": [{"idx": 0, "def": 3, "role": "ASSOC", "label": "0: a"}, {"idx": 1, "def": 4, "role": "ASSOC", "label": "0: b"}, {"idx": 2, "def": 7, "role": "ASSOC", "label": "0: c"}], "proj": null},
+    {"id": 2, "label": "Start", "type": null, "kind": "CTRL", "edges": [], "proj": null},
+    {"id": 3, "label": "#1", "type": null, "kind": "DATA", "edges": [{"idx": 0, "def": 2, "role": "ASSOC", "label": null}], "proj": null},
+    {"id": 4, "label": "#2", "type": null, "kind": "DATA", "edges": [{"idx": 0, "def": 2, "role": "ASSOC", "label": null}], "proj": null},
+    {"id": 6, "label": "#3", "type": null, "kind": "DATA", "edges": [{"idx": 0, "def": 2, "role": "ASSOC", "label": null}], "proj": null},
+    {"id": 7, "label": "+", "type": null, "kind": "DATA", "edges": [{"idx": 0, "def": 0, "role": "DATA", "label": null}, {"idx": 1, "def": 3, "role": "DATA", "label": null}, {"idx": 2, "def": 6, "role": "DATA", "label": null}], "proj": null},
+    {"id": 8, "label": "Return", "type": null, "kind": "CTRL", "edges": [{"idx": 0, "def": 2, "role": "CTRL", "label": null}, {"idx": 1, "def": 7, "role": "DATA", "label": null}], "proj": null}
+  ],
+  "groups": [
+  ]
+}
diff --git a/docs/chapter03/03-graph2.svg b/docs/chapter03/03-graph2.svg
new file mode 100644
index 00000000..3904d87e
--- /dev/null
+++ b/docs/chapter03/03-graph2.svg
@@ -0,0 +1,89 @@
+<svg aria-label="Compiler graph" width="840" height="312" xmlns="http://www.w3.org/2000/svg" viewBox="0 0 840 312" style="font-family: sans-serif;"><style>
+    html, body { height:100%; margin:0; font-family:sans-serif; }
+    .viewer { height:100%; display:grid; grid-template-rows:auto minmax(0,1fr) auto; }
+    .source { padding:8px; border-bottom:1px solid #ccc; }
+    #program { width:min(600px,80vw); vertical-align:middle; }
+    #status { margin-top:4px; }
+    #graph { min-height:0; overflow:hidden; position:relative; background:#fafbfc; }
+    #elk { width:100%; height:100%; }
+    #graph svg { display:block; }
+    .tools { display:flex; flex-wrap:wrap; align-items:center; gap:14px; margin-top:8px; font-size:12px; }
+    .hint { color:#616c78; }
+    .ctrl { color:#b63838; } .mem { color:#2867b2; } .data { color:#536477; }
+    .edge { fill:none; stroke-width:1.5; }
+    .edge.CTRL { stroke-width:2; }
+    .edge.ASSOC { stroke-dasharray:4 4; }
+    .edge.PARSER { stroke-dasharray:5 4; }
+    .parser rect { fill:#f6f0ff; stroke:#7956a5; stroke-width:1.5; stroke-dasharray:5 4; }
+    .edge.selected { stroke-width:3.5; }
+    .edge.bundle { stroke-width:4; }
+    .edge.bundle.selected { stroke-width:6; }
+    .edge-hit { fill:none; stroke:transparent; stroke-width:12; vector-effect:non-scaling-stroke; pointer-events:stroke; cursor:pointer; }
+    .edge-jump { fill:transparent; pointer-events:all; cursor:pointer; }
+    .node { cursor:pointer; }
+    .box { stroke:#758191; stroke-width:1; }
+    .node.held .box { stroke-dasharray:5 3; }
+    .node.near .box { stroke:#c18221; stroke-width:2; }
+    .node.focus .box { stroke:#9c4900; stroke-width:3; }
+    .node.selected .box { stroke:#1569b9; stroke-width:3; }
+    .node.folded .box { stroke-width:4; }
+    .node.folding .box { fill:#f4ccd7; }
+    .fold-tag { font-size:9px; font-weight:700; fill:#963751; }
+    .peep-area { fill:#fff3d9; fill-opacity:.8; stroke:#c18221; stroke-width:2; pointer-events:none; }
+    .node.peep-edit .box { stroke:#9c4900; stroke-width:3; }
+    .node.error .box { stroke:#b42318; stroke-width:4; }
+    #event.error { color:#b42318; font-weight:600; white-space:pre-wrap; overflow-wrap:anywhere; }
+    .peep-ghosts { pointer-events:none; }
+    .region-box { stroke:#9da9b8; stroke-width:1.5; }
+    .fold-btn { cursor:pointer; }
+    .fold-btn rect { fill:white; stroke:#596674; }
+    .fold-btn text { font-size:14px; fill:#152330; }
+    .fold-btn:focus rect { stroke:#1569b9; stroke-width:2; }
+    .shortcut { cursor:pointer; }
+    .shortcut path { fill:none; stroke-width:1.5; }
+    .shortcut rect { fill:#fff8ec; stroke:#b63838; stroke-dasharray:3 2; }
+    .shortcut text { font-size:11px; fill:#783030; }
+    .shortcut.selected rect, .shortcut:focus rect { stroke-width:2.5; }
+    .label { font-size:12px; fill:#152330; font-weight:600; }
+    .node-id { font-size:10px; fill:#596674; font-weight:400; }
+    .type { font-size:11px; fill:#455768; }
+    .port { stroke:#536477; stroke-width:1; }
+    .row { stroke:#b6afcf; stroke-width:1; }
+    .bind { font-size:12px; fill:#152330; }
+    .slot { font-size:10px; fill:#364352; paint-order:stroke; stroke:#fafbfc; stroke-width:3; }
+    #detail { position:absolute; top:8px; right:8px; margin:0; padding:12px; max-width:320px;
+      max-height:45%; overflow:auto; white-space:pre-wrap; overflow-wrap:anywhere;
+      background:#fffffff2; border:1px solid #bac5d0; border-radius:4px; font-size:12px; }
+    .controls { display:flex; flex-wrap:wrap; justify-content:center; align-items:center; gap:6px; padding:6px; }
+    .button { color:white; background:black; font-size:20px; min-width:30px; }
+    .button:disabled { background:grey; }
+    .count { font-size:20px; min-width:35px; text-align:center; }
+    #N { width:6ch; }
+    #scrub { width:clamp(120px,35vw,600px); }
+  </style><defs><marker id="arrow-CTRL" viewBox="0 -4 8 8" refX="8" refY="0" markerWidth="7" markerHeight="7" orient="auto-start-reverse"><path d="M0,-4L8,0L0,4Z" fill="#b63838"/></marker><marker id="arrow-DATA" viewBox="0 -4 8 8" refX="8" refY="0" markerWidth="7" markerHeight="7" orient="auto-start-reverse"><path d="M0,-4L8,0L0,4Z" fill="#536477"/></marker><marker id="arrow-MEM" viewBox="0 -4 8 8" refX="8" refY="0" markerWidth="7" markerHeight="7" orient="auto-start-reverse"><path d="M0,-4L8,0L0,4Z" fill="#2867b2"/></marker><marker id="arrow-ASSOC" viewBox="0 -4 8 8" refX="8" refY="0" markerWidth="7" markerHeight="7" orient="auto-start-reverse"><path d="M0,-4L8,0L0,4Z" fill="#9396a3"/></marker><marker id="arrow-PARSER" viewBox="0 -4 8 8" refX="8" refY="0" markerWidth="7" markerHeight="7" orient="auto-start-reverse"><path d="M0,-4L8,0L0,4Z" fill="#7956a5"/></marker></defs><rect width="100%" height="100%" fill="rgb(250, 251, 252)"/><g><g class="regions" style="opacity: 1;"/><rect class="peep-area" rx="36" style="opacity: 0;"/><g class="edges"><path class="edge ASSOC" id="e1i0" d="M236,77 C236,101 696,74 696,98" stroke="#9396a3" marker-start="url(#arrow-ASSOC)" style="opacity: 1;"><title>#1[0] → #3 · ASSOC · 0: a</title></path><path class="edge ASSOC" id="e1i1" d="M388,77 C388,101 744,74 744,98" stroke="#9396a3" marker-start="url(#arrow-ASSOC)" style="opacity: 1;"><title>#1[1] → #4 · ASSOC · 0: b</title></path><path class="edge ASSOC" id="e1i2" d="M236,181 C236,205 792,74 792,98" stroke="#9396a3" marker-start="url(#arrow-ASSOC)" style="opacity: 1;"><title>#1[2] → #7 · ASSOC · 0: c</title></path><path class="edge ASSOC" id="e3i0" d="M84,181 C84,205 236,3 236,27" stroke="#9396a3" marker-start="url(#arrow-ASSOC)" style="opacity: 1;"><title>#3[0] → #2 · ASSOC</title></path><path class="edge ASSOC" id="e4i0" d="M84,181 C84,205 388,3 388,27" stroke="#9396a3" marker-start="url(#arrow-ASSOC)" style="opacity: 1;"><title>#4[0] → #2 · ASSOC</title></path><path class="edge ASSOC" id="e6i0" d="M84,181 C84,205 540,3 540,27" stroke="#9396a3" marker-start="url(#arrow-ASSOC)" style="opacity: 1;"><title>#6[0] → #2 · ASSOC</title></path><path class="edge DATA" id="e7i1" d="M236,80 L236,128" stroke="#536477" marker-start="url(#arrow-DATA)" style="opacity: 1;"><title>#7[1] → #3 · DATA</title></path><path class="edge DATA" id="e7i2" d="M540,80 L540,85 Q540,90 535,90 L274,90 Q266,90 266,98 L266,128" stroke="#536477" marker-start="url(#arrow-DATA)" style="opacity: 1;"><title>#7[2] → #6 · DATA</title></path><path class="edge CTRL" id="e8i0" d="M84,184 L84,232" stroke="#b63838" marker-start="url(#arrow-CTRL)" style="opacity: 1;"><title>#8[0] → #2 · CTRL</title></path><path class="edge DATA" id="e8i1" d="M236,184 L236,189 Q236,194 231,194 L132,194 Q124,194 124,202 L124,232" stroke="#536477" marker-start="url(#arrow-DATA)" style="opacity: 1;"><title>#8[1] → #7 · DATA</title></path></g><g class="edge-hits"/><g class="parser" style="opacity: 1;"/><g class="nodes"><g class="node" id="n1" data-id="1" transform="translate(672,98)" style="opacity: 1;"><path class="box" d="M4,0H140Q144,0 144,4V52Q144,56 140,56H4Q0,56 0,52V4Q0,0 4,0Z" fill="#e5e0ff"/><text class="label" text-anchor="middle" x="72" y="48"><tspan>Scope</tspan><tspan class="node-id">  #1</tspan></text><text class="type" text-anchor="middle" y="35" x="72"/><title>#1 Scope
+Type not computed
+
+[0] → #3  ASSOC  0: a
+[1] → #4  ASSOC  0: b
+[2] → #7  ASSOC  0: c</title><line class="row" x1="0" x2="144" y1="30" y2="30"/><line class="row" x1="48" x2="48" y1="0" y2="30"/><line class="row" x1="96" x2="96" y1="0" y2="30"/><text class="bind" x="24" y="20" text-anchor="middle">0: a</text><text class="bind" x="72" y="20" text-anchor="middle">0: b</text><text class="bind" x="120" y="20" text-anchor="middle">0: c</text><circle class="port" cx="24" cy="0" r="3" fill="#536477"/><circle class="port" cx="72" cy="0" r="3" fill="#536477"/><circle class="port" cx="120" cy="0" r="3" fill="#536477"/><text class="slot" x="24" y="-7" text-anchor="middle">0</text><text class="slot" x="72" y="-7" text-anchor="middle">1</text><text class="slot" x="120" y="-7" text-anchor="middle">2</text></g><g class="node" id="n2" data-id="2" transform="translate(24,134)" style="opacity: 1;"><path class="box" d="M0,0H120V44H0Z" fill="#fff1c4"/><text class="label" text-anchor="middle" x="60" y="18"><tspan>Start</tspan><tspan class="node-id">  #2</tspan></text><text class="type" text-anchor="middle" y="35" x="60"/><title>#2 Start
+Type not computed
+
+</title></g><g class="node" id="n3" data-id="3" transform="translate(176,30)" style="opacity: 1;"><path class="box" d="M14,0H106Q120,0 120,14V30Q120,44 106,44H14Q0,44 0,30V14Q0,0 14,0Z" fill="#edf3f7"/><text class="label" text-anchor="middle" x="60" y="18"><tspan>#1</tspan><tspan class="node-id">  #3</tspan></text><text class="type" text-anchor="middle" y="35" x="60"/><title>#3 #1
+Type not computed
+
+[0] → #2  ASSOC</title><circle class="port" cx="60" cy="-3" r="3" fill="#536477"/><text class="slot" x="60" y="-10" text-anchor="middle">0</text></g><g class="node" id="n4" data-id="4" transform="translate(328,30)" style="opacity: 1;"><path class="box" d="M14,0H106Q120,0 120,14V30Q120,44 106,44H14Q0,44 0,30V14Q0,0 14,0Z" fill="#edf3f7"/><text class="label" text-anchor="middle" x="60" y="18"><tspan>#2</tspan><tspan class="node-id">  #4</tspan></text><text class="type" text-anchor="middle" y="35" x="60"/><title>#4 #2
+Type not computed
+
+[0] → #2  ASSOC</title><circle class="port" cx="60" cy="-3" r="3" fill="#536477"/><text class="slot" x="60" y="-10" text-anchor="middle">0</text></g><g class="node" id="n6" data-id="6" transform="translate(480,30)" style="opacity: 1;"><path class="box" d="M14,0H106Q120,0 120,14V30Q120,44 106,44H14Q0,44 0,30V14Q0,0 14,0Z" fill="#edf3f7"/><text class="label" text-anchor="middle" x="60" y="18"><tspan>#3</tspan><tspan class="node-id">  #6</tspan></text><text class="type" text-anchor="middle" y="35" x="60"/><title>#6 #3
+Type not computed
+
+[0] → #2  ASSOC</title><circle class="port" cx="60" cy="-3" r="3" fill="#536477"/><text class="slot" x="60" y="-10" text-anchor="middle">0</text></g><g class="node" id="n7" data-id="7" transform="translate(176,134)" style="opacity: 1;"><path class="box" d="M14,0H106Q120,0 120,14V30Q120,44 106,44H14Q0,44 0,30V14Q0,0 14,0Z" fill="#edf3f7"/><text class="label" text-anchor="middle" x="60" y="18"><tspan>+</tspan><tspan class="node-id">  #7</tspan></text><text class="type" text-anchor="middle" y="35" x="60"/><title>#7 +
+Type not computed
+
+[0] → —  DATA
+[1] → #3  DATA
+[2] → #6  DATA</title><circle class="port" cx="30" cy="-3" r="3" fill="white"/><circle class="port" cx="60" cy="-3" r="3" fill="#536477"/><circle class="port" cx="90" cy="-3" r="3" fill="#536477"/><text class="slot" x="30" y="-10" text-anchor="middle">0</text><text class="slot" x="60" y="-10" text-anchor="middle">1</text><text class="slot" x="90" y="-10" text-anchor="middle">2</text></g><g class="node" id="n8" data-id="8" transform="translate(44,238)" style="opacity: 1;"><path class="box" d="M0,0H120V44H0Z" fill="#fff1c4"/><text class="label" text-anchor="middle" x="60" y="18"><tspan>Return</tspan><tspan class="node-id">  #8</tspan></text><text class="type" text-anchor="middle" y="35" x="60"/><title>#8 Return
+Type not computed
+
+[0] → #2  CTRL
+[1] → #7  DATA</title><circle class="port" cx="40" cy="-3" r="3" fill="#536477"/><circle class="port" cx="80" cy="-3" r="3" fill="#536477"/><text class="slot" x="40" y="-10" text-anchor="middle">0</text><text class="slot" x="80" y="-10" text-anchor="middle">1</text></g></g><g class="region-heads" style="opacity: 1;"/><g class="shortcuts" style="opacity: 1;"/><g class="peep-ghosts" pointer-events="none"/></g></svg>
diff --git a/docs/chapter03/03-graph3.gv b/docs/chapter03/03-graph3.gv
new file mode 100644
index 00000000..791a7dc1
--- /dev/null
+++ b/docs/chapter03/03-graph3.gv
@@ -0,0 +1,37 @@
+digraph chapter03 {
+/*
+int x0=1; int y0=2; int x1=3; int y1=4; return (x0-x1)*(x0-x1) + (y0-y1)*(y0-y1);
+*/
+	rankdir=BT;
+	ordering="in";
+	concentrate="true";
+	subgraph cluster_Nodes {
+		Start2 [ shape=box style=filled fillcolor=yellow label="Start" ];
+		Con_3 [ label="#1" ];
+		Con_4 [ label="#2" ];
+		Con_20 [ label="#8" ];
+		Con_5 [ label="#3" ];
+		Return21 [ shape=box style=filled fillcolor=yellow label="Return" ];
+		Con_6 [ label="#4" ];
+	}
+	node [shape=plaintext];
+	subgraph cluster_Scope1_0 {
+		Scope1_0 [label=<
+			<TABLE BORDER="0" CELLBORDER="1" CELLSPACING="0">
+			<TR><TD BGCOLOR="cyan">0</TD><TD PORT="Scope1_0_y0">y0</TD><TD PORT="Scope1_0_x0">x0</TD><TD PORT="Scope1_0_y1">y1</TD><TD PORT="Scope1_0_x1">x1</TD></TR>
+			</TABLE>>];
+	}
+	edge [ fontname=Helvetica, fontsize=8 ];
+	Con_3 -> Start2[taillabel=0 style=dotted];
+	Con_4 -> Start2[taillabel=0 style=dotted];
+	Con_20 -> Start2[taillabel=0 style=dotted];
+	Con_5 -> Start2[taillabel=0 style=dotted];
+	Return21 -> Start2[taillabel=0 color=red];
+	Return21 -> Con_20[taillabel=1];
+	Con_6 -> Start2[taillabel=0 style=dotted];
+	edge [style=dashed color=cornflowerblue];
+	Scope1_0:"Scope1_0_y0" -> Con_4;
+	Scope1_0:"Scope1_0_x0" -> Con_3;
+	Scope1_0:"Scope1_0_y1" -> Con_6;
+	Scope1_0:"Scope1_0_x1" -> Con_5;
+}
diff --git a/docs/chapter03/03-graph3.json b/docs/chapter03/03-graph3.json
new file mode 100644
index 00000000..a6d6175a
--- /dev/null
+++ b/docs/chapter03/03-graph3.json
@@ -0,0 +1,19 @@
+{
+  "ver": 1,
+  "comp": "chapter03/docs/03-graph3.svg",
+  "step": 1,
+  "roots": [],
+  "scope": 0,
+  "nodes": [
+    {"id": 1, "label": "Scope", "type": null, "kind": "SCOPE", "edges": [{"idx": 0, "def": 4, "role": "ASSOC", "label": "0: y0"}, {"idx": 1, "def": 3, "role": "ASSOC", "label": "0: x0"}, {"idx": 2, "def": 6, "role": "ASSOC", "label": "0: y1"}, {"idx": 3, "def": 5, "role": "ASSOC", "label": "0: x1"}], "proj": null},
+    {"id": 2, "label": "Start", "type": null, "kind": "CTRL", "edges": [], "proj": null},
+    {"id": 3, "label": "#1", "type": null, "kind": "DATA", "edges": [{"idx": 0, "def": 2, "role": "ASSOC", "label": null}], "proj": null},
+    {"id": 4, "label": "#2", "type": null, "kind": "DATA", "edges": [{"idx": 0, "def": 2, "role": "ASSOC", "label": null}], "proj": null},
+    {"id": 5, "label": "#3", "type": null, "kind": "DATA", "edges": [{"idx": 0, "def": 2, "role": "ASSOC", "label": null}], "proj": null},
+    {"id": 6, "label": "#4", "type": null, "kind": "DATA", "edges": [{"idx": 0, "def": 2, "role": "ASSOC", "label": null}], "proj": null},
+    {"id": 20, "label": "#8", "type": null, "kind": "DATA", "edges": [{"idx": 0, "def": 2, "role": "ASSOC", "label": null}], "proj": null},
+    {"id": 21, "label": "Return", "type": null, "kind": "CTRL", "edges": [{"idx": 0, "def": 2, "role": "CTRL", "label": null}, {"idx": 1, "def": 20, "role": "DATA", "label": null}], "proj": null}
+  ],
+  "groups": [
+  ]
+}
diff --git a/docs/chapter03/03-graph3.svg b/docs/chapter03/03-graph3.svg
new file mode 100644
index 00000000..4c5db5e0
--- /dev/null
+++ b/docs/chapter03/03-graph3.svg
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+    html, body { height:100%; margin:0; font-family:sans-serif; }
+    .viewer { height:100%; display:grid; grid-template-rows:auto minmax(0,1fr) auto; }
+    .source { padding:8px; border-bottom:1px solid #ccc; }
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+    #status { margin-top:4px; }
+    #graph { min-height:0; overflow:hidden; position:relative; background:#fafbfc; }
+    #elk { width:100%; height:100%; }
+    #graph svg { display:block; }
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+Type not computed
+
+[0] → #4  ASSOC  0: y0
+[1] → #3  ASSOC  0: x0
+[2] → #6  ASSOC  0: y1
+[3] → #5  ASSOC  0: x1</title><line class="row" x1="0" x2="204" y1="30" y2="30"/><line class="row" x1="51" x2="51" y1="0" y2="30"/><line class="row" x1="102" x2="102" y1="0" y2="30"/><line class="row" x1="153" x2="153" y1="0" y2="30"/><text class="bind" x="25.5" y="20" text-anchor="middle">0: y0</text><text class="bind" x="76.5" y="20" text-anchor="middle">0: x0</text><text class="bind" x="127.5" y="20" text-anchor="middle">0: y1</text><text class="bind" x="178.5" y="20" text-anchor="middle">0: x1</text><circle class="port" cx="25.5" cy="0" r="3" fill="#536477"/><circle class="port" cx="76.5" cy="0" r="3" fill="#536477"/><circle class="port" cx="127.5" cy="0" r="3" fill="#536477"/><circle class="port" cx="178.5" cy="0" r="3" fill="#536477"/><text class="slot" x="25.5" y="-7" text-anchor="middle">0</text><text class="slot" x="76.5" y="-7" text-anchor="middle">1</text><text class="slot" x="127.5" y="-7" text-anchor="middle">2</text><text class="slot" x="178.5" y="-7" text-anchor="middle">3</text></g><g class="node" id="n2" data-id="2" transform="translate(24,30)" style="opacity: 1;"><path class="box" d="M0,0H120V44H0Z" fill="#fff1c4"/><text class="label" text-anchor="middle" x="60" y="18"><tspan>Start</tspan><tspan class="node-id">  #2</tspan></text><text class="type" text-anchor="middle" y="35" x="60"/><title>#2 Start
+Type not computed
+
+</title></g><g class="node" id="n3" data-id="3" transform="translate(176,30)" style="opacity: 1;"><path class="box" d="M14,0H106Q120,0 120,14V30Q120,44 106,44H14Q0,44 0,30V14Q0,0 14,0Z" fill="#edf3f7"/><text class="label" text-anchor="middle" x="60" y="18"><tspan>#1</tspan><tspan class="node-id">  #3</tspan></text><text class="type" text-anchor="middle" y="35" x="60"/><title>#3 #1
+Type not computed
+
+[0] → #2  ASSOC</title><circle class="port" cx="60" cy="-3" r="3" fill="#536477"/><text class="slot" x="60" y="-10" text-anchor="middle">0</text></g><g class="node" id="n4" data-id="4" transform="translate(328,30)" style="opacity: 1;"><path class="box" d="M14,0H106Q120,0 120,14V30Q120,44 106,44H14Q0,44 0,30V14Q0,0 14,0Z" fill="#edf3f7"/><text class="label" text-anchor="middle" x="60" y="18"><tspan>#2</tspan><tspan class="node-id">  #4</tspan></text><text class="type" text-anchor="middle" y="35" x="60"/><title>#4 #2
+Type not computed
+
+[0] → #2  ASSOC</title><circle class="port" cx="60" cy="-3" r="3" fill="#536477"/><text class="slot" x="60" y="-10" text-anchor="middle">0</text></g><g class="node" id="n5" data-id="5" transform="translate(480,30)" style="opacity: 1;"><path class="box" d="M14,0H106Q120,0 120,14V30Q120,44 106,44H14Q0,44 0,30V14Q0,0 14,0Z" fill="#edf3f7"/><text class="label" text-anchor="middle" x="60" y="18"><tspan>#3</tspan><tspan class="node-id">  #5</tspan></text><text class="type" text-anchor="middle" y="35" x="60"/><title>#5 #3
+Type not computed
+
+[0] → #2  ASSOC</title><circle class="port" cx="60" cy="-3" r="3" fill="#536477"/><text class="slot" x="60" y="-10" text-anchor="middle">0</text></g><g class="node" id="n6" data-id="6" transform="translate(632,30)" style="opacity: 1;"><path class="box" d="M14,0H106Q120,0 120,14V30Q120,44 106,44H14Q0,44 0,30V14Q0,0 14,0Z" fill="#edf3f7"/><text class="label" text-anchor="middle" x="60" y="18"><tspan>#4</tspan><tspan class="node-id">  #6</tspan></text><text class="type" text-anchor="middle" y="35" x="60"/><title>#6 #4
+Type not computed
+
+[0] → #2  ASSOC</title><circle class="port" cx="60" cy="-3" r="3" fill="#536477"/><text class="slot" x="60" y="-10" text-anchor="middle">0</text></g><g class="node" id="n20" data-id="20" transform="translate(784,30)" style="opacity: 1;"><path class="box" d="M14,0H106Q120,0 120,14V30Q120,44 106,44H14Q0,44 0,30V14Q0,0 14,0Z" fill="#edf3f7"/><text class="label" text-anchor="middle" x="60" y="18"><tspan>#8</tspan><tspan class="node-id">  #20</tspan></text><text class="type" text-anchor="middle" y="35" x="60"/><title>#20 #8
+Type not computed
+
+[0] → #2  ASSOC</title><circle class="port" cx="60" cy="-3" r="3" fill="#536477"/><text class="slot" x="60" y="-10" text-anchor="middle">0</text></g><g class="node" id="n21" data-id="21" transform="translate(44,134)" style="opacity: 1;"><path class="box" d="M0,0H120V44H0Z" fill="#fff1c4"/><text class="label" text-anchor="middle" x="60" y="18"><tspan>Return</tspan><tspan class="node-id">  #21</tspan></text><text class="type" text-anchor="middle" y="35" x="60"/><title>#21 Return
+Type not computed
+
+[0] → #2  CTRL
+[1] → #20  DATA</title><circle class="port" cx="40" cy="-3" r="3" fill="#536477"/><circle class="port" cx="80" cy="-3" r="3" fill="#536477"/><text class="slot" x="40" y="-10" text-anchor="middle">0</text><text class="slot" x="80" y="-10" text-anchor="middle">1</text></g></g><g class="region-heads" style="opacity: 1;"/><g class="shortcuts" style="opacity: 1;"/><g class="peep-ghosts" pointer-events="none"/></g></svg>
diff --git a/docs/chapter03/03-graph4.json b/docs/chapter03/03-graph4.json
new file mode 100644
index 00000000..b594eee2
--- /dev/null
+++ b/docs/chapter03/03-graph4.json
@@ -0,0 +1,17 @@
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diff --git a/docs/chapter03/03-graph4.svg b/docs/chapter03/03-graph4.svg
new file mode 100644
index 00000000..c773ef9b
--- /dev/null
+++ b/docs/chapter03/03-graph4.svg
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+    #status { margin-top:4px; }
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+    #elk { width:100%; height:100%; }
+    #graph svg { display:block; }
+    .tools { display:flex; flex-wrap:wrap; align-items:center; gap:14px; margin-top:8px; font-size:12px; }
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+      background:#fffffff2; border:1px solid #bac5d0; border-radius:4px; font-size:12px; }
+    .controls { display:flex; flex-wrap:wrap; justify-content:center; align-items:center; gap:6px; padding:6px; }
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+    .button:disabled { background:grey; }
+    .count { font-size:20px; min-width:35px; text-align:center; }
+    #N { width:6ch; }
+    #scrub { width:clamp(120px,35vw,600px); }
+  </style><defs><marker id="arrow-CTRL" viewBox="0 -4 8 8" refX="8" refY="0" markerWidth="7" markerHeight="7" orient="auto-start-reverse"><path d="M0,-4L8,0L0,4Z" fill="#b63838"/></marker><marker id="arrow-DATA" viewBox="0 -4 8 8" refX="8" refY="0" markerWidth="7" markerHeight="7" orient="auto-start-reverse"><path d="M0,-4L8,0L0,4Z" fill="#536477"/></marker><marker id="arrow-MEM" viewBox="0 -4 8 8" refX="8" refY="0" markerWidth="7" markerHeight="7" orient="auto-start-reverse"><path d="M0,-4L8,0L0,4Z" fill="#2867b2"/></marker><marker id="arrow-ASSOC" viewBox="0 -4 8 8" refX="8" refY="0" markerWidth="7" markerHeight="7" orient="auto-start-reverse"><path d="M0,-4L8,0L0,4Z" fill="#9396a3"/></marker><marker id="arrow-PARSER" viewBox="0 -4 8 8" refX="8" refY="0" markerWidth="7" markerHeight="7" orient="auto-start-reverse"><path d="M0,-4L8,0L0,4Z" fill="#7956a5"/></marker></defs><rect width="100%" height="100%" fill="rgb(250, 251, 252)"/><g><g class="regions" style="opacity: 1;"/><rect class="peep-area" rx="36" style="opacity: 0;"/><g class="edges"><path class="edge ASSOC" id="e1i0" d="M236,77 C236,101 848,74 848,98" stroke="#9396a3" marker-start="url(#arrow-ASSOC)" style="opacity: 1;"><title>#1[0] → #3 · ASSOC · 0: a</title></path><path class="edge ASSOC" id="e1i1" d="M388,77 C388,101 896,74 896,98" stroke="#9396a3" marker-start="url(#arrow-ASSOC)" style="opacity: 1;"><title>#1[1] → #4 · ASSOC · 0: b</title></path><path class="edge ASSOC" id="e1i2" d="M692,77 C692,101 944,74 944,98" stroke="#9396a3" marker-start="url(#arrow-ASSOC)" style="opacity: 1;"><title>#1[2] → #8 · ASSOC · 0: c</title></path><path class="edge ASSOC" id="e1i3" d="M540,77 C540,101 992,74 992,98" stroke="#9396a3" marker-start="url(#arrow-ASSOC)" style="opacity: 1;"><title>#1[3] → #6 · ASSOC · 1: b</title></path><path class="edge ASSOC" id="e3i0" d="M84,77 C84,101 236,3 236,27" stroke="#9396a3" marker-start="url(#arrow-ASSOC)" style="opacity: 1;"><title>#3[0] → #2 · ASSOC</title></path><path class="edge ASSOC" id="e4i0" d="M84,77 C84,101 388,3 388,27" stroke="#9396a3" marker-start="url(#arrow-ASSOC)" style="opacity: 1;"><title>#4[0] → #2 · ASSOC</title></path><path class="edge ASSOC" id="e6i0" d="M84,77 C84,101 540,3 540,27" stroke="#9396a3" marker-start="url(#arrow-ASSOC)" style="opacity: 1;"><title>#6[0] → #2 · ASSOC</title></path><path class="edge ASSOC" id="e8i0" d="M84,77 C84,101 692,3 692,27" stroke="#9396a3" marker-start="url(#arrow-ASSOC)" style="opacity: 1;"><title>#8[0] → #2 · ASSOC</title></path></g><g class="edge-hits"/><g class="parser" style="opacity: 1;"/><g class="nodes"><g class="node" id="n1" data-id="1" transform="translate(824,98)" style="opacity: 1;"><path class="box" d="M4,0H188Q192,0 192,4V52Q192,56 188,56H4Q0,56 0,52V4Q0,0 4,0Z" fill="#e5e0ff"/><text class="label" text-anchor="middle" x="96" y="48"><tspan>Scope</tspan><tspan class="node-id">  #1</tspan></text><text class="type" text-anchor="middle" y="35" x="96"/><title>#1 Scope
+Type not computed
+
+[0] → #3  ASSOC  0: a
+[1] → #4  ASSOC  0: b
+[2] → #8  ASSOC  0: c
+[3] → #6  ASSOC  1: b</title><line class="row" x1="0" x2="192" y1="30" y2="30"/><line class="row" x1="48" x2="48" y1="0" y2="30"/><line class="row" x1="96" x2="96" y1="0" y2="30"/><line class="row" x1="144" x2="144" y1="0" y2="30"/><text class="bind" x="24" y="20" text-anchor="middle">0: a</text><text class="bind" x="72" y="20" text-anchor="middle">0: b</text><text class="bind" x="120" y="20" text-anchor="middle">0: c</text><text class="bind" x="168" y="20" text-anchor="middle">1: b</text><circle class="port" cx="24" cy="0" r="3" fill="#536477"/><circle class="port" cx="72" cy="0" r="3" fill="#536477"/><circle class="port" cx="120" cy="0" r="3" fill="#536477"/><circle class="port" cx="168" cy="0" r="3" fill="#536477"/><text class="slot" x="24" y="-7" text-anchor="middle">0</text><text class="slot" x="72" y="-7" text-anchor="middle">1</text><text class="slot" x="120" y="-7" text-anchor="middle">2</text><text class="slot" x="168" y="-7" text-anchor="middle">3</text></g><g class="node" id="n2" data-id="2" transform="translate(24,30)" style="opacity: 1;"><path class="box" d="M0,0H120V44H0Z" fill="#fff1c4"/><text class="label" text-anchor="middle" x="60" y="18"><tspan>Start</tspan><tspan class="node-id">  #2</tspan></text><text class="type" text-anchor="middle" y="35" x="60"/><title>#2 Start
+Type not computed
+
+</title></g><g class="node" id="n3" data-id="3" transform="translate(176,30)" style="opacity: 1;"><path class="box" d="M14,0H106Q120,0 120,14V30Q120,44 106,44H14Q0,44 0,30V14Q0,0 14,0Z" fill="#edf3f7"/><text class="label" text-anchor="middle" x="60" y="18"><tspan>#1</tspan><tspan class="node-id">  #3</tspan></text><text class="type" text-anchor="middle" y="35" x="60"/><title>#3 #1
+Type not computed
+
+[0] → #2  ASSOC</title><circle class="port" cx="60" cy="-3" r="3" fill="#536477"/><text class="slot" x="60" y="-10" text-anchor="middle">0</text></g><g class="node" id="n4" data-id="4" transform="translate(328,30)" style="opacity: 1;"><path class="box" d="M14,0H106Q120,0 120,14V30Q120,44 106,44H14Q0,44 0,30V14Q0,0 14,0Z" fill="#edf3f7"/><text class="label" text-anchor="middle" x="60" y="18"><tspan>#2</tspan><tspan class="node-id">  #4</tspan></text><text class="type" text-anchor="middle" y="35" x="60"/><title>#4 #2
+Type not computed
+
+[0] → #2  ASSOC</title><circle class="port" cx="60" cy="-3" r="3" fill="#536477"/><text class="slot" x="60" y="-10" text-anchor="middle">0</text></g><g class="node" id="n6" data-id="6" transform="translate(480,30)" style="opacity: 1;"><path class="box" d="M14,0H106Q120,0 120,14V30Q120,44 106,44H14Q0,44 0,30V14Q0,0 14,0Z" fill="#edf3f7"/><text class="label" text-anchor="middle" x="60" y="18"><tspan>#5</tspan><tspan class="node-id">  #6</tspan></text><text class="type" text-anchor="middle" y="35" x="60"/><title>#6 #5
+Type not computed
+
+[0] → #2  ASSOC</title><circle class="port" cx="60" cy="-3" r="3" fill="#536477"/><text class="slot" x="60" y="-10" text-anchor="middle">0</text></g><g class="node" id="n8" data-id="8" transform="translate(632,30)" style="opacity: 1;"><path class="box" d="M14,0H106Q120,0 120,14V30Q120,44 106,44H14Q0,44 0,30V14Q0,0 14,0Z" fill="#edf3f7"/><text class="label" text-anchor="middle" x="60" y="18"><tspan>#6</tspan><tspan class="node-id">  #8</tspan></text><text class="type" text-anchor="middle" y="35" x="60"/><title>#8 #6
+Type not computed
+
+[0] → #2  ASSOC</title><circle class="port" cx="60" cy="-3" r="3" fill="#536477"/><text class="slot" x="60" y="-10" text-anchor="middle">0</text></g></g><g class="region-heads" style="opacity: 1;"/><g class="shortcuts" style="opacity: 1;"/><g class="peep-ghosts" pointer-events="none"/></g></svg>
diff --git a/docs/chapter03/03-graph5.json b/docs/chapter03/03-graph5.json
new file mode 100644
index 00000000..476ad586
--- /dev/null
+++ b/docs/chapter03/03-graph5.json
@@ -0,0 +1,17 @@
+{
+  "ver": 1,
+  "comp": "chapter03/docs/03-graph5.svg",
+  "step": 1,
+  "roots": [],
+  "scope": 0,
+  "nodes": [
+    {"id": 1, "label": "Scope", "type": null, "kind": "SCOPE", "edges": [{"idx": 0, "def": 3, "role": "ASSOC", "label": "0: a"}, {"idx": 1, "def": 4, "role": "ASSOC", "label": "0: b"}, {"idx": 2, "def": 11, "role": "ASSOC", "label": "0: c"}, {"idx": 3, "def": 9, "role": "ASSOC", "label": "1: e"}], "proj": null},
+    {"id": 2, "label": "Start", "type": null, "kind": "CTRL", "edges": [], "proj": null},
+    {"id": 3, "label": "#1", "type": null, "kind": "DATA", "edges": [{"idx": 0, "def": 2, "role": "ASSOC", "label": null}], "proj": null},
+    {"id": 4, "label": "#2", "type": null, "kind": "DATA", "edges": [{"idx": 0, "def": 2, "role": "ASSOC", "label": null}], "proj": null},
+    {"id": 9, "label": "#6", "type": null, "kind": "DATA", "edges": [{"idx": 0, "def": 2, "role": "ASSOC", "label": null}], "proj": null},
+    {"id": 11, "label": "#7", "type": null, "kind": "DATA", "edges": [{"idx": 0, "def": 2, "role": "ASSOC", "label": null}], "proj": null}
+  ],
+  "groups": [
+  ]
+}
diff --git a/docs/chapter03/03-graph5.svg b/docs/chapter03/03-graph5.svg
new file mode 100644
index 00000000..a62d03bb
--- /dev/null
+++ b/docs/chapter03/03-graph5.svg
@@ -0,0 +1,84 @@
+<svg aria-label="Compiler graph" width="1040" height="178" xmlns="http://www.w3.org/2000/svg" viewBox="0 0 1040 178" style="font-family: sans-serif;"><style>
+    html, body { height:100%; margin:0; font-family:sans-serif; }
+    .viewer { height:100%; display:grid; grid-template-rows:auto minmax(0,1fr) auto; }
+    .source { padding:8px; border-bottom:1px solid #ccc; }
+    #program { width:min(600px,80vw); vertical-align:middle; }
+    #status { margin-top:4px; }
+    #graph { min-height:0; overflow:hidden; position:relative; background:#fafbfc; }
+    #elk { width:100%; height:100%; }
+    #graph svg { display:block; }
+    .tools { display:flex; flex-wrap:wrap; align-items:center; gap:14px; margin-top:8px; font-size:12px; }
+    .hint { color:#616c78; }
+    .ctrl { color:#b63838; } .mem { color:#2867b2; } .data { color:#536477; }
+    .edge { fill:none; stroke-width:1.5; }
+    .edge.CTRL { stroke-width:2; }
+    .edge.ASSOC { stroke-dasharray:4 4; }
+    .edge.PARSER { stroke-dasharray:5 4; }
+    .parser rect { fill:#f6f0ff; stroke:#7956a5; stroke-width:1.5; stroke-dasharray:5 4; }
+    .edge.selected { stroke-width:3.5; }
+    .edge.bundle { stroke-width:4; }
+    .edge.bundle.selected { stroke-width:6; }
+    .edge-hit { fill:none; stroke:transparent; stroke-width:12; vector-effect:non-scaling-stroke; pointer-events:stroke; cursor:pointer; }
+    .edge-jump { fill:transparent; pointer-events:all; cursor:pointer; }
+    .node { cursor:pointer; }
+    .box { stroke:#758191; stroke-width:1; }
+    .node.held .box { stroke-dasharray:5 3; }
+    .node.near .box { stroke:#c18221; stroke-width:2; }
+    .node.focus .box { stroke:#9c4900; stroke-width:3; }
+    .node.selected .box { stroke:#1569b9; stroke-width:3; }
+    .node.folded .box { stroke-width:4; }
+    .node.folding .box { fill:#f4ccd7; }
+    .fold-tag { font-size:9px; font-weight:700; fill:#963751; }
+    .peep-area { fill:#fff3d9; fill-opacity:.8; stroke:#c18221; stroke-width:2; pointer-events:none; }
+    .node.peep-edit .box { stroke:#9c4900; stroke-width:3; }
+    .node.error .box { stroke:#b42318; stroke-width:4; }
+    #event.error { color:#b42318; font-weight:600; white-space:pre-wrap; overflow-wrap:anywhere; }
+    .peep-ghosts { pointer-events:none; }
+    .region-box { stroke:#9da9b8; stroke-width:1.5; }
+    .fold-btn { cursor:pointer; }
+    .fold-btn rect { fill:white; stroke:#596674; }
+    .fold-btn text { font-size:14px; fill:#152330; }
+    .fold-btn:focus rect { stroke:#1569b9; stroke-width:2; }
+    .shortcut { cursor:pointer; }
+    .shortcut path { fill:none; stroke-width:1.5; }
+    .shortcut rect { fill:#fff8ec; stroke:#b63838; stroke-dasharray:3 2; }
+    .shortcut text { font-size:11px; fill:#783030; }
+    .shortcut.selected rect, .shortcut:focus rect { stroke-width:2.5; }
+    .label { font-size:12px; fill:#152330; font-weight:600; }
+    .node-id { font-size:10px; fill:#596674; font-weight:400; }
+    .type { font-size:11px; fill:#455768; }
+    .port { stroke:#536477; stroke-width:1; }
+    .row { stroke:#b6afcf; stroke-width:1; }
+    .bind { font-size:12px; fill:#152330; }
+    .slot { font-size:10px; fill:#364352; paint-order:stroke; stroke:#fafbfc; stroke-width:3; }
+    #detail { position:absolute; top:8px; right:8px; margin:0; padding:12px; max-width:320px;
+      max-height:45%; overflow:auto; white-space:pre-wrap; overflow-wrap:anywhere;
+      background:#fffffff2; border:1px solid #bac5d0; border-radius:4px; font-size:12px; }
+    .controls { display:flex; flex-wrap:wrap; justify-content:center; align-items:center; gap:6px; padding:6px; }
+    .button { color:white; background:black; font-size:20px; min-width:30px; }
+    .button:disabled { background:grey; }
+    .count { font-size:20px; min-width:35px; text-align:center; }
+    #N { width:6ch; }
+    #scrub { width:clamp(120px,35vw,600px); }
+  </style><defs><marker id="arrow-CTRL" viewBox="0 -4 8 8" refX="8" refY="0" markerWidth="7" markerHeight="7" orient="auto-start-reverse"><path d="M0,-4L8,0L0,4Z" fill="#b63838"/></marker><marker id="arrow-DATA" viewBox="0 -4 8 8" refX="8" refY="0" markerWidth="7" markerHeight="7" orient="auto-start-reverse"><path d="M0,-4L8,0L0,4Z" fill="#536477"/></marker><marker id="arrow-MEM" viewBox="0 -4 8 8" refX="8" refY="0" markerWidth="7" markerHeight="7" orient="auto-start-reverse"><path d="M0,-4L8,0L0,4Z" fill="#2867b2"/></marker><marker id="arrow-ASSOC" viewBox="0 -4 8 8" refX="8" refY="0" markerWidth="7" markerHeight="7" orient="auto-start-reverse"><path d="M0,-4L8,0L0,4Z" fill="#9396a3"/></marker><marker id="arrow-PARSER" viewBox="0 -4 8 8" refX="8" refY="0" markerWidth="7" markerHeight="7" orient="auto-start-reverse"><path d="M0,-4L8,0L0,4Z" fill="#7956a5"/></marker></defs><rect width="100%" height="100%" fill="rgb(250, 251, 252)"/><g><g class="regions" style="opacity: 1;"/><rect class="peep-area" rx="36" style="opacity: 0;"/><g class="edges"><path class="edge ASSOC" id="e1i0" d="M236,77 C236,101 848,74 848,98" stroke="#9396a3" marker-start="url(#arrow-ASSOC)" style="opacity: 1;"><title>#1[0] → #3 · ASSOC · 0: a</title></path><path class="edge ASSOC" id="e1i1" d="M388,77 C388,101 896,74 896,98" stroke="#9396a3" marker-start="url(#arrow-ASSOC)" style="opacity: 1;"><title>#1[1] → #4 · ASSOC · 0: b</title></path><path class="edge ASSOC" id="e1i2" d="M692,77 C692,101 944,74 944,98" stroke="#9396a3" marker-start="url(#arrow-ASSOC)" style="opacity: 1;"><title>#1[2] → #11 · ASSOC · 0: c</title></path><path class="edge ASSOC" id="e1i3" d="M540,77 C540,101 992,74 992,98" stroke="#9396a3" marker-start="url(#arrow-ASSOC)" style="opacity: 1;"><title>#1[3] → #9 · ASSOC · 1: e</title></path><path class="edge ASSOC" id="e3i0" d="M84,77 C84,101 236,3 236,27" stroke="#9396a3" marker-start="url(#arrow-ASSOC)" style="opacity: 1;"><title>#3[0] → #2 · ASSOC</title></path><path class="edge ASSOC" id="e4i0" d="M84,77 C84,101 388,3 388,27" stroke="#9396a3" marker-start="url(#arrow-ASSOC)" style="opacity: 1;"><title>#4[0] → #2 · ASSOC</title></path><path class="edge ASSOC" id="e9i0" d="M84,77 C84,101 540,3 540,27" stroke="#9396a3" marker-start="url(#arrow-ASSOC)" style="opacity: 1;"><title>#9[0] → #2 · ASSOC</title></path><path class="edge ASSOC" id="e11i0" d="M84,77 C84,101 692,3 692,27" stroke="#9396a3" marker-start="url(#arrow-ASSOC)" style="opacity: 1;"><title>#11[0] → #2 · ASSOC</title></path></g><g class="edge-hits"/><g class="parser" style="opacity: 1;"/><g class="nodes"><g class="node" id="n1" data-id="1" transform="translate(824,98)" style="opacity: 1;"><path class="box" d="M4,0H188Q192,0 192,4V52Q192,56 188,56H4Q0,56 0,52V4Q0,0 4,0Z" fill="#e5e0ff"/><text class="label" text-anchor="middle" x="96" y="48"><tspan>Scope</tspan><tspan class="node-id">  #1</tspan></text><text class="type" text-anchor="middle" y="35" x="96"/><title>#1 Scope
+Type not computed
+
+[0] → #3  ASSOC  0: a
+[1] → #4  ASSOC  0: b
+[2] → #11  ASSOC  0: c
+[3] → #9  ASSOC  1: e</title><line class="row" x1="0" x2="192" y1="30" y2="30"/><line class="row" x1="48" x2="48" y1="0" y2="30"/><line class="row" x1="96" x2="96" y1="0" y2="30"/><line class="row" x1="144" x2="144" y1="0" y2="30"/><text class="bind" x="24" y="20" text-anchor="middle">0: a</text><text class="bind" x="72" y="20" text-anchor="middle">0: b</text><text class="bind" x="120" y="20" text-anchor="middle">0: c</text><text class="bind" x="168" y="20" text-anchor="middle">1: e</text><circle class="port" cx="24" cy="0" r="3" fill="#536477"/><circle class="port" cx="72" cy="0" r="3" fill="#536477"/><circle class="port" cx="120" cy="0" r="3" fill="#536477"/><circle class="port" cx="168" cy="0" r="3" fill="#536477"/><text class="slot" x="24" y="-7" text-anchor="middle">0</text><text class="slot" x="72" y="-7" text-anchor="middle">1</text><text class="slot" x="120" y="-7" text-anchor="middle">2</text><text class="slot" x="168" y="-7" text-anchor="middle">3</text></g><g class="node" id="n2" data-id="2" transform="translate(24,30)" style="opacity: 1;"><path class="box" d="M0,0H120V44H0Z" fill="#fff1c4"/><text class="label" text-anchor="middle" x="60" y="18"><tspan>Start</tspan><tspan class="node-id">  #2</tspan></text><text class="type" text-anchor="middle" y="35" x="60"/><title>#2 Start
+Type not computed
+
+</title></g><g class="node" id="n3" data-id="3" transform="translate(176,30)" style="opacity: 1;"><path class="box" d="M14,0H106Q120,0 120,14V30Q120,44 106,44H14Q0,44 0,30V14Q0,0 14,0Z" fill="#edf3f7"/><text class="label" text-anchor="middle" x="60" y="18"><tspan>#1</tspan><tspan class="node-id">  #3</tspan></text><text class="type" text-anchor="middle" y="35" x="60"/><title>#3 #1
+Type not computed
+
+[0] → #2  ASSOC</title><circle class="port" cx="60" cy="-3" r="3" fill="#536477"/><text class="slot" x="60" y="-10" text-anchor="middle">0</text></g><g class="node" id="n4" data-id="4" transform="translate(328,30)" style="opacity: 1;"><path class="box" d="M14,0H106Q120,0 120,14V30Q120,44 106,44H14Q0,44 0,30V14Q0,0 14,0Z" fill="#edf3f7"/><text class="label" text-anchor="middle" x="60" y="18"><tspan>#2</tspan><tspan class="node-id">  #4</tspan></text><text class="type" text-anchor="middle" y="35" x="60"/><title>#4 #2
+Type not computed
+
+[0] → #2  ASSOC</title><circle class="port" cx="60" cy="-3" r="3" fill="#536477"/><text class="slot" x="60" y="-10" text-anchor="middle">0</text></g><g class="node" id="n9" data-id="9" transform="translate(480,30)" style="opacity: 1;"><path class="box" d="M14,0H106Q120,0 120,14V30Q120,44 106,44H14Q0,44 0,30V14Q0,0 14,0Z" fill="#edf3f7"/><text class="label" text-anchor="middle" x="60" y="18"><tspan>#6</tspan><tspan class="node-id">  #9</tspan></text><text class="type" text-anchor="middle" y="35" x="60"/><title>#9 #6
+Type not computed
+
+[0] → #2  ASSOC</title><circle class="port" cx="60" cy="-3" r="3" fill="#536477"/><text class="slot" x="60" y="-10" text-anchor="middle">0</text></g><g class="node" id="n11" data-id="11" transform="translate(632,30)" style="opacity: 1;"><path class="box" d="M14,0H106Q120,0 120,14V30Q120,44 106,44H14Q0,44 0,30V14Q0,0 14,0Z" fill="#edf3f7"/><text class="label" text-anchor="middle" x="60" y="18"><tspan>#7</tspan><tspan class="node-id">  #11</tspan></text><text class="type" text-anchor="middle" y="35" x="60"/><title>#11 #7
+Type not computed
+
+[0] → #2  ASSOC</title><circle class="port" cx="60" cy="-3" r="3" fill="#536477"/><text class="slot" x="60" y="-10" text-anchor="middle">0</text></g></g><g class="region-heads" style="opacity: 1;"/><g class="shortcuts" style="opacity: 1;"/><g class="peep-ghosts" pointer-events="none"/></g></svg>
diff --git a/docs/chapter03/Makefile b/docs/chapter03/Makefile
new file mode 100644
index 00000000..6fa0f057
--- /dev/null
+++ b/docs/chapter03/Makefile
@@ -0,0 +1 @@
+include ../../graph/docs.mk
diff --git a/docs/chapter03/README.ja.md b/docs/chapter03/README.ja.md
new file mode 100644
index 00000000..a0fd8546
--- /dev/null
+++ b/docs/chapter03/README.ja.md
@@ -0,0 +1,167 @@
+# 第3章: 変数宣言
+
+[English](README.md) | 日本語
+
+この文書は [原文](README.md) の日本語訳です。
+
+[前の章: 第2章](../chapter02/README.ja.md) |
+[次の章: 第4章](../chapter04/README.ja.md)
+
+# 目次
+
+1. [中間表現の拡張](#中間表現の拡張)
+2. [シンボルテーブル](#シンボルテーブル)
+3. [ScopeNode](#scopenode)
+4. [実例](#実例)
+5. [ピープホール最適化の有効化](#ピープホール最適化の有効化)
+
+[linear](https://github.com/SeaOfNodes/Simple/tree/linear) ブランチの直線的な Git のリビジョン履歴で [この章](https://github.com/SeaOfNodes/Simple/tree/linear-chapter03) を読み、前の章と [比較](https://github.com/SeaOfNodes/Simple/compare/linear-chapter02...linear-chapter03) することもできます。
+
+この章では、変数宣言を可能にするために言語の文法を拡張します。これにより、次のように書けます。
+
+```
+int a=1;
+int b=2;
+int c=0;
+{
+    int b=3;
+    c=a+b;
+}
+return c;
+```
+
+この章の [完全な言語文法](03-grammar.ja.md) はこちらです。
+
+## 中間表現の拡張
+
+この章では次のノードを導入します。
+
+| ノード名 | 種類 | 説明 | 入力 | 値 |
+|-----------|--------------|--------------------------------|---------------------------------|-------|
+| Scope | シンボルテーブル | グラフ内のスコープを表す | 変数を定義するすべてのノード | なし |
+
+前の章までのすべてのノードも引き続き使います。
+
+## シンボルテーブル
+
+変数宣言とレキシカルスコープをサポートするため、パーサーにシンボルテーブルを導入します。シンボルテーブルは名前をノードに対応付けます。
+
+シンボルテーブルの *スタック* を管理します。新しいレキシカルスコープが作られると、新しいシンボルテーブルをスタックにプッシュします。スコープを抜けると、スタックの最上部にあるシンボルテーブルをポップします。
+
+名前を宣言すると、現在のシンボルテーブルに追加されます。名前に代入すると、最も新しいシンボルテーブル内の対応付けが更新されます。名前を参照すると、シンボルテーブル内でその対応付けを検索します。検索はレキシカルな順序で、シンボルテーブルのスタックをさかのぼります。
+
+## ScopeNode
+
+ScopeNode は、レキシカルスコープの実装に使うシンボルテーブルのスタックをカプセル化します。
+
+* レキシカルスコープ内の名前が参照するノードは、ScopeNode の入力になります。これにより ScopeNode がそれらの値の利用側となり、そのレキシカルスコープが生きている間、値も生存します。レキシカルスコープが終わると、これらの入力は取り除かれます。ピープホール最適化は死んだノードを削除し、新しいノードは生成直後には実質的に死んでいるため、これは極めて重要です。
+* 分岐を実装する [第5章](../chapter05/README.ja.md) では、分岐点で ScopeNode を複製し、分岐が合流するときにマージします。これにより、それぞれの分岐で名前を独立して更新できます。マージ地点では、異なる値になった名前に Phi ノードが必要です。
+* [第7章](../chapter07/README.ja.md) では、バックエッジからの Phi を扱う追加のロジックを導入します。
+* ScopeNode は、[第4章](../chapter04/README.ja.md) からは制御トークン、[第10章](../chapter10/README.ja.md) からはメモリ全体など、ほかの値の追跡にも使われます。これらには特別な名前の束縛を使い、それぞれの名前を分岐をまたいで追跡し、マージ地点でマージします。
+* [第10章](../chapter10/README.ja.md) では ScopeNode を拡張し、各名前の宣言された型も管理します。
+
+実装上、各シンボルテーブルは `HashMap<String,Integer>` で表します。`String` は変数名で、`Integer` は ScopeNode の入力へのインデックスです。名前に対応するノードを取得するには、まずシンボルテーブルを調べ、次に ScopeNode の入力から必要なノードを取得します。シンボルテーブルのスタックは `Stack<HashMap<String,Integer>>` で表します。
+
+レキシカルスコープを抜けるときは、そのスコープを表すシンボルテーブルをスタックからポップするだけでなく、対応する入力ノードも取り除きます。変数の式が Scope の対応付けのためだけに存在している場合（たとえば、その変数を使うコードをパーサーが解析する「かもしれない」ために保持していた場合）、この時点で式は死にます。
+
+```
+  int a=1;
+  {
+      int b=a*a*a;
+  }  // When this scope closes and ends, b (and the cube of a) dies
+  return a;
+```
+
+可視化では、ScopeNode を独立した紫色の箱で示します。各束縛には、そのレキシカルスコープの階層をラベルとして付けます。シンボルテーブルの各変数から、グラフ内の定義ノードへ向かうエッジを示します。
+
+ScopeNode はデータノードでも制御ノードでもありません。シンボルテーブルの管理と名前の検索のための補助機構であり、どこに Phi ノードが必要かを決める重要な役割を果たします。ノードとして表すことで、Sea of Nodes の定義・使用（def-use）アーキテクチャを利用して、スコープ内の値の生存性を維持できます。
+
+ScopeNode に出力はありません。
+
+## 実例
+
+次のコードから得られる出力を示します。
+
+```
+01      int a=1;
+02      int b=2;
+03      int c=0;
+04      {
+05          int b=3;
+07          c=a+b;
+08      }
+09      return c;
+```
+
+* この例の解析を始めるとき、階層0のシンボルテーブルから始めます。変数 `a`、`b`、`c` をこのテーブルに登録します。
+* 4行目では、入れ子のスコープを開始します。この時点で新しいシンボルテーブルを階層1にプッシュします。
+* 5行目では、変数 `b` を宣言します。`b` を階層1のシンボルテーブルに登録し、2行目の同名の変数を隠します。
+* 7行目では、変数 `c` を更新します。変数の検索では、階層0のシンボルテーブルにある `c` が見つかります。
+
+次の模式図は、定数畳み込み前の変数の束縛と算術演算を示します。コンパイラはグラフを構築しながらピープホール最適化を適用するため、この例の実際の結果は `return 4;` です。
+
+![グラフ1](./03-graph1.svg)
+
+この図は ScopeNode の束縛をスコープの階層とともに示します。`b` の2つの束縛は、異なるレキシカルスコープに属しています。
+
+* 8行目で入れ子のスコープを抜けると、階層1のシンボルテーブルをポップします。
+* 9行目では、グラフは次のようになります。
+
+![グラフ2](./03-graph2.svg)
+
+この時点では、シンボルテーブルが1つだけ存在することがわかります。
+
+プログラムの実行中には同じ階層のスコープが複数存在することもあります。ただし、各スコープ階層にはシンボルテーブルを1つしか保持できないため、同時に有効になるのは1つだけです。
+
+たとえば、次のようになります。
+
+```
+01   int a=1;
+02   int b=2;
+03   int c=0;
+04   {
+05       int b=5;
+06       c=a+b;
+08   }
+09   {
+10       int e=6;
+11       c = a+e;
+13   }
+14    return c;
+```
+
+ここでは `(04-08)` と `(09-13)` の2つのスコープは同じ階層にあります。
+
+```java
+public final Stack<HashMap<String, Integer>> _scopes;
+```
+
+`_scopes` スタックは入れ子のスコープを保持します。インデックス0が最上位の（グローバル）スコープを表し、より大きなインデックスがより深い入れ子のスコープを表します。ポップすると現在のスコープを返し、外側のスコープに移ります。各インデックスと対応するスコープには、直接の1対1の対応があります。
+
+最初の入れ子のスコープ（04-08）:
+
+![グラフ4](./03-graph4.svg)
+
+2つ目の入れ子のスコープ（09-13）:
+
+![グラフ5](./03-graph5.svg)
+
+* どちらの場合も、スコープの深さを表すインデックスは1です。
+
+## ピープホール最適化の有効化
+
+ピープホール最適化を有効にすると、パーサーはすべての式を定数に簡約できます。次の例がその様子をよく示しています。
+
+```
+01      int x0=1;
+02      int y0=2;
+03      int x1=3;
+04      int y1=4;
+05      return (x0-x1)*(x0-x1) + (y0-y1)*(y0-y1);
+```
+
+この例のグラフを次に示します。
+
+![グラフ2](./03-graph3.svg)
+
+Return ノードのデータ値は定数 `8` です！ 解析が終わって階層0のスコープが取り除かれると、`return 8` だけが残ります。
diff --git a/docs/chapter03/README.md b/docs/chapter03/README.md
new file mode 100644
index 00000000..82393094
--- /dev/null
+++ b/docs/chapter03/README.md
@@ -0,0 +1,193 @@
+# Chapter 3: Variable Declarations
+
+English | [日本語](README.ja.md)
+
+[Previous: Chapter 2](../chapter02/README.md) |
+[Next: Chapter 4](../chapter04/README.md)
+
+# Table of Contents
+
+1. [Extensions to Intermediate Representation](#extensions-to-intermediate-representation)
+2. [Symbol Tables](#symbol-tables)
+3. [ScopeNode](#scopenode)
+4. [Demonstration](#demonstration)
+5. [Enabling peephole optimizations](#enabling-peephole-optimizations)
+
+You can also read [this chapter](https://github.com/SeaOfNodes/Simple/tree/linear-chapter03) in a linear Git revision history on the [linear](https://github.com/SeaOfNodes/Simple/tree/linear) branch and [compare](https://github.com/SeaOfNodes/Simple/compare/linear-chapter02...linear-chapter03) it to the previous chapter.
+
+In this chapter we extend the language grammar to allow variable declarations. This allows us to write:
+
+```
+int a=1;
+int b=2;
+int c=0;
+{
+    int b=3;
+    c=a+b;
+}
+return c;
+```
+
+Here is the [complete language grammar](03-grammar.md) for this chapter.
+
+
+## Extensions to Intermediate Representation
+
+In this chapter we introduce:
+
+| Node Name | Type         | Description                    | Inputs                          | Value |
+|-----------|--------------|--------------------------------|---------------------------------|-------|
+| Scope     | Symbol Table | Represents scopes in the graph | All nodes that define variables | None  |
+
+and keep all nodes from prior chapters.
+
+## Symbol Tables
+
+To support variable declarations and lexical scopes, we introduce symbol tables
+in the parser. A symbol table maps names to nodes.
+
+We maintain a *stack* of symbol tables.
+When a new lexical scope is created we push a new symbol table to the stack;
+when scope exits the topmost symbol table is popped from the stack.
+
+Declaring a name adds it to the current symbol table.  If a name is assigned
+to, then its mapping in the most recent symbol table is updated.  If a name is
+accessed, its mapping is looked up in the symbol tables.  The lookup goes up
+the stack of symbol tables, in lexical order.
+
+## ScopeNode
+
+A ScopeNode encapsulates the stack of symbol tables that are used to implement lexical scopes.
+
+* The nodes referenced by the names in a lexical scope become inputs to the
+  ScopeNode; this makes ScopeNode a user of these values, thus keeping them
+  alive while a particular lexical scope is alive.  When the lexical scope
+  ends, those inputs are removed. This is crucial because peepholes will remove
+  dead Nodes and every new Node is effectively dead at the instant of creation.
+* In [Chapter 5](../chapter05/README.md) when we implement branches, the ScopeNode gets duplicated at a branch point and then gets merged when the branch joins. This allows
+  the names to evolve in each branch independently. At the merge point, names that have diverged require a Phi node.
+* In [Chapter 7](../chapter07/README.md) additional logic is deployed for handling Phis from back edges.
+* The ScopeNode is used to track some other values such as the Control token starting from [Chapter 4](../chapter04/README.md), and whole memory starting from [Chapter 10](../chapter10/README.md). Special name bindings are used
+  for these, and each name is tracked across branches and then merged at merge points.
+* In [Chapter 10](../chapter10/README.md) the ScopeNode is enhanced to also maintain the declared type for each name.
+
+From an implementation standpoint, each symbol table is represented as a `HashMap<String,Integer>`, where the `String` is the variable name, and the `Integer` is an index into the inputs of the
+ScopeNode. To access the Node associated with a name, first the symbol table is consulted, and then the ScopeNode's inputs to find the required Node.
+The stack of symbol tables is represented as `Stack<HashMap<String,Integer>>`.
+
+When a lexical scope is exited, we not only pop the symbol table representing the
+scope from the stack, but also remove the relevant input nodes.  If the variable's expression
+only exists for the Scope mapping (e.g., "just in case" the Parser parses code
+that uses the variable) this is when the expression dies:
+```
+  int a=1;
+  {
+      int b=a*a*a;
+  }  // When this scope closes and ends, b (and the cube of a) dies
+  return a;
+```
+
+
+In the visualization, we show the ScopeNode in a separate purple box. Each
+binding is labelled with its lexical scope level. We show the edge from each
+variable in the symbol table to the defining
+Node in the graph.
+
+The ScopeNode is neither a Data Node nor a Control Node; it really is a utility for maintaining symbol tables, name lookups, plays a crucial role in deciding where Phi nodes are required.
+Representing it as a Node allows us to leverage the Sea of Nodes def-use architecture to maintain liveness of values in scope.
+
+A ScopeNode has no outputs.
+
+## Demonstration
+
+We show the output from the following code.
+
+```
+01      int a=1;
+02      int b=2;
+03      int c=0;
+04      {
+05          int b=3;
+07          c=a+b;
+08      }
+09      return c;
+```
+
+* When we start parsing the example above, we start with a symbol table (at level 0).
+The variables `a`, `b`, and `c` are registered in this table.
+* On line 4, we start a nested scope. At this point, a new symbol table is pushed (at level 1).
+* On line 5, a variable `b` is declared. `b` is registered in the symbol table at level 1. This then
+hides the variable with the same name on line 2.
+* On line 7, we update the variable `c`. Variable lookup will find it in the symbol table at level 0.
+The schematic below shows the variable bindings and arithmetic before constant
+folding. The compiler applies peepholes as it builds the graph, so the actual
+result of this example is `return 4;`.
+
+![Graph1](./03-graph1.svg)
+
+The diagram shows the ScopeNode's bindings with their scope levels. The two
+bindings for `b` belong to different lexical scopes.
+
+* When we exit the nested scope on line 8, the symbol table at level 1 is popped.
+* At line 9, our graph looks like this:
+
+![Graph2](./03-graph2.svg)
+
+As we see, only 1 symbol table is present at this point.
+
+We can also have multiple scopes at the same level during the execution of the program,
+but only one will be active at a time because the symbol table can only hold one symbol table
+for each scope level.
+
+For example:
+```
+01   int a=1;
+02   int b=2;
+03   int c=0;
+04   {
+05       int b=5;
+06       c=a+b;
+08   }
+09   {
+10       int e=6;
+11       c = a+e;
+13   }
+14    return c;
+```
+Here both scopes starting from `(04-08)` and `(09-13)` are at the same level:
+```java
+public final Stack<HashMap<String, Integer>> _scopes;
+```
+The `_scopes` stack holds nested scopes, with index 0 representing the highest (global)
+scope and deeper indices representing more nested scopes.
+Popping returns the current scope and moves to the outer one.
+There is a direct one-to-one mapping between each index and its corresponding scope.
+
+The first nested scope (04-08):
+
+![Graph4](./03-graph4.svg)
+
+The second nested scope (09-13):
+
+![Graph5](./03-graph5.svg)
+
+ - In both cases the index which represents the depth of the scope is 1.
+## Enabling peephole optimizations
+
+Once we enable peephole optimizations, the parser is able to reduce all the expressions down to a
+constant. This is illustrated nicely below.
+
+```
+01      int x0=1;
+02      int y0=2;
+03      int x1=3;
+04      int y1=4;
+05      return (x0-x1)*(x0-x1) + (y0-y1)*(y0-y1);
+```
+
+The graph for the example above is displayed below.
+
+![Graph2](./03-graph3.svg)
+
+The return node has the constant `8` as its data value!  When the parsing ends
+and the scope at level 0 is removed, only the `return 8` remains.
diff --git a/src/main/java/com/seaofnodes/simple/Parser.java b/src/main/java/com/seaofnodes/simple/Parser.java
index f59b0f25..e6cb84f8 100644
--- a/src/main/java/com/seaofnodes/simple/Parser.java
+++ b/src/main/java/com/seaofnodes/simple/Parser.java
@@ -5,6 +5,8 @@ import com.seaofnodes.graph.GraphObserver;
 import com.seaofnodes.simple.node.*;
 import com.seaofnodes.simple.type.*;
 
+import java.util.*;
+
 /**
  * The Parser converts a Simple source program to the Sea of Nodes intermediate
  * representation directly in one pass. There is no intermediate Abstract
@@ -32,33 +34,73 @@ public class Parser {
     // The Lexer.  Thin wrapper over a byte[] buffer with a cursor.
     private final Lexer _lexer;
 
+    /**
+     * Stack of lexical scopes, each scope is a symbol table that binds
+     * variable names to Nodes.  The top of this stack represents current scope.
+     */
+    public ScopeNode _scope;
+
+    /**
+     * List of keywords disallowed as identifiers
+     */
+    private final HashSet<String> KEYWORDS = new HashSet<>(){{
+            add("int");
+            add("return");
+        }};
+
 
     public Parser(String source) {
         _lexer = new Lexer(source);
         PARSER = this;
         Node.reset();
+        _scope = new ScopeNode();
         START = new StartNode();
     }
 
     String src() { return new String( _lexer._input ); }
 
     public ReturnNode parse() {
-        var ret = (ReturnNode) parseStatement();
+        var ret = (ReturnNode) parseBlock();
         if (!_lexer.isEOF()) throw error("Syntax error, unexpected " + _lexer.getAnyNextToken());
         return ret;
     }
 
     /**
+     * Parses a block
+     *
+     * <pre>
+     *     '{' statements '}'
+     * </pre>
+     * Does not parse the opening or closing '{}'
+     * @return a {@link Node} or {@code null}
+     */
+    private Node parseBlock() {
+        // Enter a new scope
+        _scope.push();
+        Node n = null;
+        while (!peek('}') && !_lexer.isEOF()) {
+            Node n0 = parseStatement();
+            if (n0 != null) n = n0; // Empty statements can return null
+        };
+        // Exit scope
+        _scope.pop();
+        return n;
+    }
+
+    /**
      * Parses a statement
      *
      * <pre>
-     *     returnStatement
+     *     returnStatement | declStatement | blockStatement | expressionStatement
      * </pre>
      * @return a {@link Node} or {@code null}
      */
     private Node parseStatement() {
-        if (matchx("return")) return parseReturn();
-        throw errorSyntax("a statement");
+        if (matchx("return")  ) return parseReturn();
+        else if (matchx("int")) return parseDecl();
+        else if (match ("{"  )) return require(parseBlock(),"}");
+        else if (matchx(";")) return null; // Empty statement
+        else return parseExpressionStatement();
     }
 
     /**
@@ -74,6 +116,43 @@ public class Parser {
         return new ReturnNode(START, expr).peephole();
     }
 
+
+
+    /**
+     * Parses an expression statement
+     *
+     * <pre>
+     *     name '=' expression ';'
+     * </pre>
+     * @return an expression {@link Node}, never {@code null}
+     */
+    private Node parseExpressionStatement() {
+        var name = requireId();
+        require("=");
+        var expr = require(parseExpression(), ";");
+        if( _scope.update(name, expr)==null )
+            throw error("Undefined name '" + name + "'");
+        return expr;
+    }
+
+    /**
+     * Parses a declStatement
+     *
+     * <pre>
+     *     'int' name = expression ';'
+     * </pre>
+     * @return an expression {@link Node}, never {@code null}
+     */
+    private Node parseDecl() {
+        // Type is 'int' for now
+        var name = requireId();
+        require("=");
+        var expr = require(parseExpression(), ";");
+        if( _scope.define(name,expr) == null )
+            throw error("Redefining name '" + name + "'");
+        return expr;
+    }
+
     /**
      * Parse an expression of the form:
      *
@@ -138,7 +217,11 @@ public class Parser {
     private Node parsePrimary() {
         if( _lexer.isNumber() ) return parseIntegerLiteral();
         if( match("(") ) return require(parseExpression(), ")");
-        throw errorSyntax("integer literal");
+        String name = _lexer.matchId();
+        if( name == null) throw errorSyntax("an identifier or expression");
+        Node n = _scope.lookup(name);
+        if( n!=null ) return n;
+        throw error("Undefined name '" + name + "'");
     }
 
     /**
@@ -159,6 +242,15 @@ public class Parser {
     private boolean match (String syntax) { return _lexer.match (syntax); }
     // Match must be "exact", not be followed by more id letters
     private boolean matchx(String syntax) { return _lexer.matchx(syntax); }
+    // Return true and do NOT skip if 'ch' is next
+    private boolean peek(char ch) { return _lexer.peek(ch); }
+
+    // Require and return an identifier
+    private String requireId() {
+        String id = _lexer.matchId();
+        if (id != null && !KEYWORDS.contains(id) ) return id;
+        throw error("Expected an identifier, found '"+id+"'");
+    }
 
     // Require an exact match
     private void require(String syntax) { require(null, syntax); }
@@ -256,6 +348,17 @@ public class Parser {
             return false;
         }
 
+        private boolean peek(char ch) {
+            skipWhiteSpace();
+            return peek()==ch;
+        }
+
+        // Return an identifier or null
+        String matchId() {
+            skipWhiteSpace();
+            return isIdStart(peek()) ? parseId() : null;
+        }
+
         // Used for errors
         String getAnyNextToken() {
             if (isEOF()) return "";
diff --git a/src/main/java/com/seaofnodes/simple/node/Node.java b/src/main/java/com/seaofnodes/simple/node/Node.java
index 3c0c3905..54687b2e 100644
--- a/src/main/java/com/seaofnodes/simple/node/Node.java
+++ b/src/main/java/com/seaofnodes/simple/node/Node.java
@@ -83,6 +83,13 @@ public abstract class Node extends BaseNode<Node> {
      * Change a <em>def</em> into a Node.  Keeps the edges correct, by removing
      * the corresponding <em>use->def</em> edge.  This may make the original
      * <em>def</em> go dead.  This function is co-recursive with {@link #kill}.
+     * <p>
+
+     * This method is the normal path for altering a Node, because it does the
+     * proper default edge maintenance.  It also <em>immediately</em> kills
+     * Nodes that lose their last use; at times care must be taken to avoid
+     * killing Nodes that are being used without having an output Node.  This
+     * definitely happens in the middle of recursive {@link #peephole} calls.
      *
      * @param idx which def to set
      * @param new_def the new definition
@@ -105,6 +112,22 @@ public abstract class Node extends BaseNode<Node> {
         return new_def;
     }
 
+    /**
+     * Add a new def to an existing Node.  Keep the edges correct by
+     * adding the corresponding <em>def->use</em> edge.
+     *
+     * @param new_def the new definition, appended to the end of existing definitions
+     * @return new_def for flow coding
+     */
+    Node addDef(Node new_def) {
+        // Add use->def edge
+        _inputs.add(new_def);
+        // If new def is not null, add the corresponding def->use edge
+        if( new_def != null )
+            new_def.addUse(this);
+        return new_def;
+    }
+
     // Breaks the edge invariants, used temporarily
     protected <N extends Node> void addUse(N n) { _outputs.add(n); }
 
@@ -116,16 +139,25 @@ public abstract class Node extends BaseNode<Node> {
         return _outputs.size() == 0;
     }
 
+    // Shortcut for "popping" n nodes.  A "pop" is basically a
+    // set_def(last,null) followed by lowering the nIns() count.
+    void popN(int n) {
+        for( int i=0; i<n; i++ ) {
+            Node old_def = _inputs.removeLast();
+            if( old_def != null &&     // If it exists and
+                old_def.delUse(this) ) // If we removed the last use, the old def is now dead
+                old_def.kill();        // Kill old def
+        }
+    }
+
     /**
      * Kill a Node with no <em>uses</em>, by setting all of its <em>defs</em>
      * to null.  This may recursively kill more Nodes and is basically dead
-     * code elimination.  This function is co-recursive with {@link #setDef}.
+     * code elimination.  This function is co-recursive with {@link #popN}.
      */
     public void kill( ) {
         assert isUnused();      // Has no uses, so it is dead
-        for( int i=0; i<nIns(); i++ )
-            setDef(i,null);  // Set all inputs to null, recursively killing unused Nodes
-        _inputs.clear();
+        popN(nIns());          // Set all inputs to null, recursively killing unused Nodes
         _type=null;             // Flag as dead
         assert isDead();        // Really dead now
     }
@@ -197,4 +229,24 @@ public abstract class Node extends BaseNode<Node> {
      * Node unique id generator, and is done as part of making a new Parser.
      */
     public static void reset() { UNIQUE_ID = 1; }
+
+    /**
+     * Debugging utility to find a Node by index
+     */
+    public Node find(int nid) { return _find(new BitSet(),nid); }
+    private Node _find(BitSet visit, int nid) {
+        if( _nid==nid ) return this;
+        if( visit.get(_nid) ) return null;
+        visit.set(_nid);
+        for( Node def : _inputs )
+            if( def!=null ) {
+                Node rez = def._find(visit,nid);
+                if( rez != null ) return rez;
+            }
+        for( Node use : _outputs ) {
+            Node rez = use._find(visit,nid);
+            if( rez != null ) return rez;
+        }
+        return null;
+    }
 }
diff --git a/src/main/java/com/seaofnodes/simple/node/ScopeNode.java b/src/main/java/com/seaofnodes/simple/node/ScopeNode.java
new file mode 100644
index 00000000..95c25391
--- /dev/null
+++ b/src/main/java/com/seaofnodes/simple/node/ScopeNode.java
@@ -0,0 +1,130 @@
+package com.seaofnodes.simple.node;
+
+import com.seaofnodes.print.ExprPrinter;
+
+import com.seaofnodes.simple.type.Type;
+
+import java.util.*;
+
+/**
+ * The Scope node is purely a parser helper - it tracks names to nodes with a
+ * stack of scopes.
+ * @see <a href="file:../../../../../../../../chapter03/README.md">chapter03/README.md</a>
+ */
+public class ScopeNode extends Node {
+
+    /**
+     * A Stack of symbol tables; a symbol table is a map from names to node indices.
+     */
+    public final Stack<HashMap<String, Integer>> _scopes;
+
+
+    // A new ScopeNode
+    public ScopeNode() {
+        _scopes = new Stack<>();
+        _type = Type.BOTTOM;
+    }
+
+
+    @Override public String label() { return "Scope"; }
+
+    @Override
+    protected ExprPrinter<Node> _print1(ExprPrinter<Node> p) {
+        p.p(label());
+        for( HashMap<String,Integer> scope : _scopes ) {
+            p.p("[");
+            boolean first=true;
+            for( String name : scope.keySet() ) {
+                if( !first ) p.p(", ");
+                first=false;
+                p.p(name).p(":");
+                Node n = in(scope.get(name));
+                if( n==null ) p.p("null");
+                else p.n(n);
+            }
+            p.p("]");
+        }
+        return p;
+    }
+
+    /**
+     * Recover the names for all variable bindings.
+     * The result is an array of names that is aligned with the
+     * inputs to the Node.
+     * <p>
+     * This is an expensive operation.
+     */
+    public String[] reverseNames() {
+        String[] names = new String[nIns()];
+        for( HashMap<String,Integer> syms : _scopes )
+            for( String name : syms.keySet() )
+                names[syms.get(name)] = name;
+        return names;
+    }
+
+    @Override public Type compute() { return Type.BOTTOM; }
+
+    @Override public Node idealize() { return null; }
+
+    public void push() { _scopes.push(new HashMap<>());  }
+    public void pop() { popN(_scopes.pop().size());  }
+
+    /**
+     * Create a new name in the current scope
+     */
+    public Node define( String name, Node n ) {
+        HashMap<String,Integer> syms = _scopes.lastElement();
+        if( syms.put(name,nIns()) != null )
+            return null;        // Double define
+        return addDef(n);
+    }
+    /**
+     * Lookup a name in all scopes starting from most deeply nested.
+     * <p>
+     * @param name Name to be looked up
+     * @see #update(String, Node, int)
+     */
+    public Node lookup( String name ) { return update(name,null,_scopes.size()-1);  }
+    /**
+     * If the name is present in any scope, then redefine else null
+     * <p>
+     * @param name Name being redefined
+     * @param n    The node to bind to the name
+     */
+    public Node update( String name, Node n ) { return update(name,n,_scopes.size()-1); }
+    /**
+     * Both recursive lookup and update.
+     * <p>
+     * A shared implementation allows us to create lazy phis both during
+     * lookups and updates; the lazy phi creation is part of chapter 8.
+     *
+     * @param name  Name whose binding is being updated or looked up
+     * @param n     If null, do a lookup, else update binding
+     * @param nestingLevel The starting nesting level
+     * @return node being looked up, or the one that was updated
+     */
+    private Node update( String name, Node n, int nestingLevel ) {
+        if( nestingLevel<0 ) return null;  // Missed in all scopes, not found
+        var syms = _scopes.get(nestingLevel); // Get the symbol table for nesting level
+        var idx = syms.get(name);
+        if( idx == null ) return update(name,n,nestingLevel-1); // Not found in this scope, recursively look in parent scope
+        Node old = in(idx);
+        // If n is null we are looking up rather than updating, hence return existing value
+        return n==null ? old : setDef(idx,n);
+    }
+
+    public Node ctrl() { return in(0); }
+
+    /**
+     * The ctrl of a ScopeNode is always bound to the currently active
+     * control node in the graph, via a special name '$ctrl' that is not
+     * a valid identifier in the language grammar and hence cannot be
+     * referenced in Simple code.
+     *
+     * @param n The node to be bound to '$ctrl'
+     *
+     * @return Node that was bound
+     */
+    public Node ctrl(Node n) { return setDef(0,n); }
+
+}
diff --git a/src/main/java/com/seaofnodes/simple/print/SimpleGraphAdapter.java b/src/main/java/com/seaofnodes/simple/print/SimpleGraphAdapter.java
index 8f2f31ec..c97aaf55 100644
--- a/src/main/java/com/seaofnodes/simple/print/SimpleGraphAdapter.java
+++ b/src/main/java/com/seaofnodes/simple/print/SimpleGraphAdapter.java
@@ -5,16 +5,21 @@ import com.seaofnodes.graph.GraphSnapshot.*;
 import com.seaofnodes.simple.node.*;
 import com.seaofnodes.simple.node.Node;
 
-/** Chapter 2's view of the IR; browser, transport and layout are shared. */
+/** Chapter 3's view of the IR; browser, transport and layout are shared. */
 public class SimpleGraphAdapter extends GraphAdapter<Node> {
 
+    @Override protected String[] edgeNames(Node n) {
+        return n instanceof ScopeNode scope && n.nIns()!=0 ? scope.reverseNames() : null;
+    }
+
     @Override protected Kind kind(Node n) {
+        if( n instanceof ScopeNode ) return Kind.SCOPE;
         if( n instanceof StartNode ) return Kind.CTRL;
         return n.isCFG() ? Kind.CTRL : Kind.DATA;
     }
 
     @Override protected Role role(Node n, int i) {
-        if( n instanceof ConstantNode ) return Role.ASSOC;
+        if( n instanceof ScopeNode || n instanceof ConstantNode ) return Role.ASSOC;
         if( i == 0 ) return Role.CTRL;
         return Role.DATA;
     }
diff --git a/src/main/java/com/seaofnodes/simple/print/SimpleGraphObserver.java b/src/main/java/com/seaofnodes/simple/print/SimpleGraphObserver.java
index a17bf796..2dc5d844 100644
--- a/src/main/java/com/seaofnodes/simple/print/SimpleGraphObserver.java
+++ b/src/main/java/com/seaofnodes/simple/print/SimpleGraphObserver.java
@@ -7,7 +7,7 @@ import com.seaofnodes.simple.node.Node;
 import java.util.ArrayList;
 import java.io.IOException;
 
-/** Chapter 2's compilation context; capture and event bookkeeping are shared. */
+/** Chapter 3's compilation context; capture and event bookkeeping are shared. */
 public class SimpleGraphObserver extends GraphCapture<Node> {
     private Parser _parser;
     private Node _ret;
@@ -30,6 +30,7 @@ public class SimpleGraphObserver extends GraphCapture<Node> {
         _parser = null;
         _ret = null;
     }
+    @Override protected Node scope() { return _parser._scope; }
     @Override protected void roots(ArrayList<Node> roots) {
         roots.add(Parser.START);
         roots.add(_ret);
diff --git a/src/test/java/com/seaofnodes/simple/Chapter01Test.java b/src/test/java/com/seaofnodes/simple/Chapter01Test.java
index 49edfb5b..311ca23b 100644
--- a/src/test/java/com/seaofnodes/simple/Chapter01Test.java
+++ b/src/test/java/com/seaofnodes/simple/Chapter01Test.java
@@ -40,7 +40,7 @@ public class Chapter01Test {
             new Parser("ret").parse();
             fail();
         } catch( RuntimeException e ) {
-            assertEquals("Syntax error, expected a statement: ret",e.getMessage());
+            assertEquals("Syntax error, expected =: ",e.getMessage());
         }
     }
 
@@ -82,7 +82,7 @@ public class Chapter01Test {
             new Parser("return100").parse();
             fail();
         } catch( RuntimeException e ) {
-            assertEquals("Syntax error, expected a statement: return100",e.getMessage());
+            assertEquals("Syntax error, expected =: ",e.getMessage());
         }
     }
 
diff --git a/src/test/java/com/seaofnodes/simple/Chapter03Test.java b/src/test/java/com/seaofnodes/simple/Chapter03Test.java
new file mode 100644
index 00000000..9a7dda5d
--- /dev/null
+++ b/src/test/java/com/seaofnodes/simple/Chapter03Test.java
@@ -0,0 +1,68 @@
+package com.seaofnodes.simple;
+
+import com.seaofnodes.simple.node.*;
+import org.junit.Test;
+
+import static org.junit.Assert.*;
+
+public class Chapter03Test {
+
+    @Test
+    public void testVarDecl() {
+        Parser parser = new Parser("int a=1; return a;");
+        ReturnNode ret = parser.parse();
+        assertEquals("return 1;", ret.print());
+    }
+
+    @Test
+    public void testVarAdd() {
+        Parser parser = new Parser("int a=1; int b=2; return a+b;");
+        ReturnNode ret = parser.parse();
+        assertEquals("return 3;", ret.print());
+    }
+
+    @Test
+    public void testVarScope() {
+        Parser parser = new Parser("int a=1; int b=2; int c=0; { int b=3; c=a+b; } return c;");
+        ReturnNode ret = parser.parse();
+        assertEquals("return 4;", ret.print());
+    }
+
+    @Test
+    public void testVarDist() {
+        Parser parser = new Parser("int x0=1; int y0=2; int x1=3; int y1=4; return (x0-x1)*(x0-x1) + (y0-y1)*(y0-y1);");
+        ReturnNode ret = parser.parse();
+        assertEquals("return 8;", ret.print());
+    }
+
+    @Test
+    public void testSelfAssign() {
+        try {
+            new Parser("int a=a; return a;").parse();
+            fail();
+        } catch( RuntimeException e ) {
+            assertEquals("Undefined name 'a'",e.getMessage());
+        }
+    }
+
+    @Test
+    public void testRedeclareVar() {
+        try {
+            new Parser("int a=1; int b=2; int c=0; int b=3; c=a+b;").parse();
+            fail();
+        } catch( RuntimeException e ) {
+            assertEquals("Redefining name 'b'",e.getMessage());
+        }
+    }
+
+    @Test
+    public void testBad1() {
+        try {
+            new Parser("int a=1; int b=2; int c=0; { int b=3; c=a+b;").parse();
+            fail();
+        } catch( RuntimeException e ) {
+            assertEquals("Syntax error, expected }: ",e.getMessage());
+        }
+    }
+
+}
author	Cliff Click <cliffc@acm.org>	2023-10-01 18:01:54 +0100
committer	Cliff Click <cliffc@acm.org>	2026-10-08 16:52:27 -0700
commit	2892fa548f7ab10ca146b76b3a608aacccf780d9 (patch)
tree	4fce21888a1561a72aba5c0ccf9165fa4d8a1ccb
parent	4968424d5aceefcf5ab6af1c6c0f7d23b9cbfadf (diff)
download	Simple-2892fa548f7ab10ca146b76b3a608aacccf780d9.tar.gz Simple-2892fa548f7ab10ca146b76b3a608aacccf780d9.zip