Add shared graph viewer to all chapters

21 files changed, 44 insertions, 313 deletions

diff --git a/chapter04/Makefile b/chapter04/Makefile
index 931ad8ef..060e0cfd 100644
--- a/chapter04/Makefile
+++ b/chapter04/Makefile
@@ -36,10 +36,7 @@ CLZDIR:= build/classes
 main_javas   := $(wildcard $(SRC)/$(SIMPLE)/*java $(SRC)/$(SIMPLE)/*/*java)
 test_javas   := $(wildcard $(TST)/$(SIMPLE)/*java $(TST)/$(SIMPLE)/*/*java)
 main_classes := $(patsubst $(SRC)/%java,$(CLZDIR)/main/%class,$(main_javas))
-# Compile the common adapter into this chapter without copying its sources.
-GRAPH_DIR := $(firstword $(wildcard ../graph graph))
-graph_javas := $(wildcard $(GRAPH_DIR)/src/main/java/com/seaofnodes/graph/*.java)
-main_javas += $(graph_javas)
+include $(firstword $(wildcard ../graph/graph.mk graph/graph.mk))
 test_classes := $(patsubst $(TST)/%java,$(CLZDIR)/test/%class,$(test_javas))
 test_cp      := $(patsubst $(TST)/$(SIMPLE)/%.java,com.seaofnodes.simple.%,$(wildcard $(TST)/$(SIMPLE)/*Test.java))
 classes = $(main_classes) $(test_classes)
@@ -81,10 +78,6 @@ fuzzer: $(default_targets)
 	@echo "fuzzing " $(test_cp)
 	@$(JVM) org.junit.runner.JUnitCore com.seaofnodes.simple.FuzzerWrap
 
-.PHONY: view
-view: build
-	java -ea -cp "$(CLZDIR)/main" com.seaofnodes.simple.print.JSViewer
-
 
 .PHONY: clean
 clean:
@@ -109,4 +102,4 @@ tags:	$(main_javas) $(test_javas)
 	@rm -f TAGS
 	@$(CTAGS) -e --recurse=yes --extra=+q --fields=+fksaiS $(SRC) $(TST)
 
-include ../build-support/chapter-release.mk
+include $(firstword $(wildcard ../build-support/chapter-release.mk build-support/chapter-release.mk))
diff --git a/chapter04/README.md b/chapter04/README.md
index 272d0b8d..2c7f7e9c 100644
--- a/chapter04/README.md
+++ b/chapter04/README.md
@@ -108,7 +108,7 @@ tests can (and do) pass in other integer values by calling `new Parser` with
 an argument:
 
 ```java
-Parser parser = new Parser("return arg; #showGraph;", TypeInteger.constant(2));
+Parser parser = new Parser("return arg; ", TypeInteger.constant(2));
 ```
 
 The graph:
@@ -151,7 +151,7 @@ public final Node peephole( ) {
 If you don't pass an argument you get `TypeInteger.BOT`
 
 ```java 
-    Parser parser = new Parser("return arg; #showGraph;");
+    Parser parser = new Parser("return arg; ");
     ...
     
 public Parser(String source) {
diff --git a/chapter04/docs/04-grammar.md b/chapter04/docs/04-grammar.md
index 48facd4c..0600679e 100644
--- a/chapter04/docs/04-grammar.md
+++ b/chapter04/docs/04-grammar.md
@@ -12,12 +12,8 @@ statement
     | declStatement
     | blockStatment
     | expressionStatement
-    | metaStatement
     ;
 
-metaStatement
-    : '#showGraph' ';'
-    ;
 
 expressionStatement
     : IDENTIFIER '=' expression ';'
diff --git a/chapter04/docs/04-post-peephole.gv b/chapter04/docs/04-post-peephole.gv
index 0a9f8e93..b893874f 100644
--- a/chapter04/docs/04-post-peephole.gv
+++ b/chapter04/docs/04-post-peephole.gv
@@ -1,6 +1,6 @@
 digraph chapter04 {
 /*
-return 1+arg+2; #showGraph;
+return 1+arg+2;
 */
 	rankdir=BT;
 	ordering="in";
diff --git a/chapter04/docs/04-pre-peephole.gv b/chapter04/docs/04-pre-peephole.gv
index aefd81c4..d0d7cb0c 100644
--- a/chapter04/docs/04-pre-peephole.gv
+++ b/chapter04/docs/04-pre-peephole.gv
@@ -1,6 +1,6 @@
 digraph chapter04 {
 /*
-return 1+arg+2; #showGraph;
+return 1+arg+2;
 */
 	rankdir=BT;
 	ordering="in";
diff --git a/chapter04/src/main/java/com/seaofnodes/simple/GraphVisualizer.java b/chapter04/src/main/java/com/seaofnodes/simple/GraphVisualizer.java
deleted file mode 100644
index 62b434f3..00000000
--- a/chapter04/src/main/java/com/seaofnodes/simple/GraphVisualizer.java
+++ /dev/null
@@ -1,212 +0,0 @@
-package com.seaofnodes.simple;
-
-import com.seaofnodes.simple.node.*;
-
-import java.util.*;
-
-/**
- * Simple visualizer that outputs GraphViz dot format.
- * The dot output must be saved to a file and run manually via dot to generate the SVG output.
- * Currently, this is done manually.
- */
-public class GraphVisualizer {
-
-    public String generateDotOutput(Parser parser) {
-
-        // Since the graph has cycles, we need to create a flat list of all the
-        // nodes in the graph.
-        Collection<Node> all = findAll(parser);
-        StringBuilder sb = new StringBuilder();
-        sb.append("digraph chapter04 {\n");
-        sb.append("/*\n");
-        sb.append(parser.src());
-        sb.append("\n*/\n");
-
-        // To keep the Scopes below the graph and pointing up into the graph we
-        // need to group the Nodes in a subgraph cluster, and the scopes into a
-        // different subgraph cluster.  THEN we can draw edges between the
-        // scopes and nodes.  If we try to cross subgraph cluster borders while
-        // still making the subgraphs DOT gets confused.
-        sb.append("\trankdir=BT;\n"); // Force Nodes before Scopes
-
-        // Preserve node input order
-        sb.append("\tordering=\"in\";\n");
-
-        // Merge multiple edges hitting the same node.  Makes common shared
-        // nodes much prettier to look at.
-        sb.append("\tconcentrate=\"true\";\n");
-
-        // Just the Nodes first, in a cluster no edges
-        nodes(sb, all);
-
-        // Now the scopes, in a cluster no edges
-        scopes(sb, parser._scope);
-
-        // Walk the Node edges
-        nodeEdges(sb, all);
-
-        // Walk the Scope edges
-        scopeEdges(sb, parser._scope);
-
-        sb.append("}\n");
-        return sb.toString();
-    }
-
-
-    private void nodes(StringBuilder sb, Collection<Node> all) {
-        // Just the Nodes first, in a cluster no edges
-        sb.append("\tsubgraph cluster_Nodes {\n"); // Magic "cluster_" in the subgraph name
-        for( Node n : all ) {
-            if( n instanceof ProjNode || n instanceof ScopeNode )
-                continue; // Do not emit, rolled into MultiNode or Scope cluster already
-            sb.append("\t\t").append(n.uniqueName()).append(" [ ");
-            String lab = n.glabel();
-            if( n instanceof MultiNode ) {
-                // Make a box with the MultiNode on top, and all the projections on the bottom
-                sb.append("shape=plaintext label=<\n");
-                sb.append("\t\t\t<TABLE BORDER=\"0\" CELLBORDER=\"1\" CELLSPACING=\"0\" CELLPADDING=\"4\">\n");
-                sb.append("\t\t\t<TR><TD BGCOLOR=\"yellow\">").append(lab).append("</TD></TR>\n");
-                sb.append("\t\t\t<TR>");
-                boolean doProjTable = false;
-                for( Node use : n._outputs ) {
-                    if( use instanceof ProjNode proj ) {
-                        if (!doProjTable) {
-                            doProjTable = true;
-                            sb.append("<TD>").append("\n");
-                            sb.append("\t\t\t\t<TABLE BORDER=\"0\" CELLBORDER=\"1\" CELLSPACING=\"0\">").append("\n");
-                            sb.append("\t\t\t\t<TR>");
-                        }
-                        sb.append("<TD PORT=\"p").append(proj._idx).append("\"");
-                        if( proj.isCFG() ) sb.append(" BGCOLOR=\"yellow\"");
-                        sb.append(">").append(proj.glabel()).append("</TD>");
-                    }
-                }
-                if (doProjTable) {
-                    sb.append("</TR>").append("\n");
-                    sb.append("\t\t\t\t</TABLE>").append("\n");
-                    sb.append("\t\t\t</TD>");
-                }
-                sb.append("</TR>\n");
-                sb.append("\t\t\t</TABLE>>\n\t\t");
-
-            } else {
-                // control nodes have box shape
-                // other nodes are ellipses, i.e. default shape
-                if( n.isCFG() )
-                    sb.append("shape=box style=filled fillcolor=yellow ");
-                sb.append("label=\"").append(lab).append("\" ");
-            }
-            sb.append("];\n");
-        }
-        sb.append("\t}\n");     // End Node cluster
-    }
-
-    private void scopes( StringBuilder sb, ScopeNode scopenode) {
-        sb.append("\tnode [shape=plaintext];\n");
-        int level=0;
-        for( HashMap<String,Integer> scope : scopenode._scopes ) {
-            String scopeName = makeScopeName(scopenode, level);
-            sb.append("\tsubgraph cluster_").append(scopeName).append(" {\n"); // Magic "cluster_" in the subgraph name
-            sb.append("\t\t").append(scopeName).append(" [label=<\n");
-            sb.append("\t\t\t<TABLE BORDER=\"0\" CELLBORDER=\"1\" CELLSPACING=\"0\">\n");
-            // Add the scope level
-            sb.append("\t\t\t<TR><TD BGCOLOR=\"cyan\">").append(level).append("</TD>");
-            for( String name : scope.keySet() )
-                sb.append("<TD PORT=\"").append(makePortName(scopeName, name)).append("\">").append(name).append("</TD>");
-            sb.append("</TR>\n");
-            sb.append("\t\t\t</TABLE>>];\n");
-            level++;
-        }
-        // Scope clusters nest, so the graphics shows the nested scopes, so
-        // they are not closed as they are printed; so they just keep nesting.
-        // We close them all at once here.
-        sb.append( "\t}\n".repeat( level ) ); // End all Scope clusters
-    }
-
-    private String makeScopeName(ScopeNode sn, int level) { return sn.uniqueName() + "_" + level; }
-    private String makePortName(String scopeName, String varName) { return scopeName + "_" + varName; }
-
-    // Walk the node edges
-    private void nodeEdges(StringBuilder sb, Collection<Node> all) {
-        // All them edge labels
-        sb.append("\tedge [ fontname=Helvetica, fontsize=8 ];\n");
-        for( Node n : all ) {
-            // Do not display the Constant->Start edge;
-            // ProjNodes handled by Multi;
-            // ScopeNodes are done separately
-            if( n instanceof ConstantNode || n instanceof ProjNode || n instanceof ScopeNode )
-                continue;
-            int i=0;
-            for( Node def : n._inputs ) {
-                if( def != null ) {
-                    // Most edges land here use->def
-                    sb.append('\t').append(n.uniqueName()).append(" -> ");
-                    if( def instanceof ProjNode proj ) {
-                        String mname = proj.ctrl().uniqueName();
-                        sb.append(mname).append(":p").append(proj._idx);
-                    } else sb.append(def.uniqueName());
-                    // Number edges, so we can see how they track
-                    sb.append("[taillabel=").append(i);
-                    // control edges are colored red
-                    if( def.isCFG() )
-                        sb.append(" color=red");
-                    sb.append("];\n");
-                }
-                i++;
-            }
-        }
-    }
-
-    // Walk the scope edges
-    private void scopeEdges( StringBuilder sb, ScopeNode scopenode ) {
-        sb.append("\tedge [style=dashed color=cornflowerblue];\n");
-        int level=0;
-        for( HashMap<String,Integer> scope : scopenode._scopes ) {
-            String scopeName = makeScopeName(scopenode, level);
-            for( String name : scope.keySet() ) {
-                Node def = scopenode.in(scope.get(name));
-                if( def==null ) continue;
-                sb.append("\t")
-                  .append(scopeName).append(":")
-                  .append('"').append(makePortName(scopeName, name)).append('"') // wrap port name with quotes because $ctrl is not valid unquoted
-                  .append(" -> ");
-                if( def instanceof ProjNode proj ) {
-                    String mname = proj.ctrl().uniqueName();
-                    sb.append(mname).append(":p").append(proj._idx);
-                } else sb.append(def.uniqueName());
-                sb.append(";\n");
-            }
-            level++;
-        }
-    }
-
-    /**
-     * Finds all nodes in the graph.
-     */
-    private Collection<Node> findAll(Parser parser) {
-        final StartNode start = Parser.START;
-        final HashMap<Integer, Node> all = new HashMap<>();
-        for( Node n : start._outputs )
-            walk(all, n);
-        // Scan symbol tables
-        for( HashMap<String,Integer> scope : parser._scope._scopes )
-            for (Integer i : scope.values())
-                walk(all, parser._scope.in(i));
-        return all.values();
-    }
-
-    /**
-     * Walk a subgraph and populate distinct nodes in the all list.
-     */
-    private void walk(HashMap<Integer, Node> all, Node n) {
-        if(n == null ) return;
-        if (all.get(n._nid) != null) return; // Been there, done that
-        all.put(n._nid, n);
-        for (Node c : n._inputs)
-            if (c != null)
-                walk(all, c);
-        for (Node c : n._outputs)
-            if (c != null)
-                walk(all, c);
-    }
-}
diff --git a/chapter04/src/main/java/com/seaofnodes/simple/Parser.java b/chapter04/src/main/java/com/seaofnodes/simple/Parser.java
index 360a7be9..487afee9 100644
--- a/chapter04/src/main/java/com/seaofnodes/simple/Parser.java
+++ b/chapter04/src/main/java/com/seaofnodes/simple/Parser.java
@@ -27,7 +27,6 @@ public class Parser {
     // Current compilation context, like START; the observer belongs to the parser.
     public static Parser PARSER;
     public GraphObserver<Node> _obs;
-    public ReturnNode _ret;
     public int pos() { return _lexer._position; }
 
     // The Lexer.  Thin wrapper over a byte[] buffer with a cursor.
@@ -73,8 +72,7 @@ public class Parser {
 
     private Node ctrl(Node n) { return _scope.ctrl(n); }
 
-    public ReturnNode parse() { return parse(false); }
-    public ReturnNode parse(boolean show) {
+    public ReturnNode parse() {
         // Enter a new scope for the initial control and arguments
         _scope.push();
         _scope.define(ScopeNode.CTRL, new ProjNode(START, 0, ScopeNode.CTRL).peephole());
@@ -82,9 +80,6 @@ public class Parser {
         var ret = (ReturnNode) parseBlock();
         _scope.pop();
         if (!_lexer.isEOF()) throw error("Syntax error, unexpected " + _lexer.getAnyNextToken());
-        if( show ) showGraph();
-        _ret = ret;
-        if( _obs != null ) _obs.phase("Parse");
         return ret;
     }
 
@@ -103,7 +98,7 @@ public class Parser {
         Node n = null;
         while (!peek('}') && !_lexer.isEOF()) {
             Node n0 = parseStatement();
-            if (n0 != null) n = n0; // Allow null returns from eg showGraph
+            if (n0 != null) n = n0; // Empty statements can return null
         };
         // Exit scope
         _scope.pop();
@@ -122,7 +117,6 @@ public class Parser {
         if (matchx("return")  ) return parseReturn();
         else if (matchx("int")) return parseDecl();
         else if (match ("{"  )) return require(parseBlock(),"}");
-        else if (matchx("#showGraph")) return require(showGraph(),";");
         else if (matchx(";")) return null; // Empty statement
         else return parseExpressionStatement();
     }
@@ -143,14 +137,7 @@ public class Parser {
         return ret;
     }
 
-    /**
-     * Dumps out the node graph
-     * @return {@code null}
-     */
-    private Node showGraph() {
-        System.out.println(new GraphVisualizer().generateDotOutput(this));
-        return null;
-    }
+
 
     /**
      * Parses an expression statement
diff --git a/chapter04/src/main/java/com/seaofnodes/simple/node/AddNode.java b/chapter04/src/main/java/com/seaofnodes/simple/node/AddNode.java
index 7e08a207..f568416c 100644
--- a/chapter04/src/main/java/com/seaofnodes/simple/node/AddNode.java
+++ b/chapter04/src/main/java/com/seaofnodes/simple/node/AddNode.java
@@ -7,8 +7,6 @@ public class AddNode extends Node {
 
     @Override public String label() { return "Add"; }
 
-    @Override public String glabel() { return "+"; }
-
     @Override
     StringBuilder _print1(StringBuilder sb) {
         in(1)._print0(sb.append("("));
diff --git a/chapter04/src/main/java/com/seaofnodes/simple/node/BoolNode.java b/chapter04/src/main/java/com/seaofnodes/simple/node/BoolNode.java
index 05495790..af0d22b7 100644
--- a/chapter04/src/main/java/com/seaofnodes/simple/node/BoolNode.java
+++ b/chapter04/src/main/java/com/seaofnodes/simple/node/BoolNode.java
@@ -15,9 +15,6 @@ abstract public class BoolNode extends Node {
     public String label() { return getClass().getSimpleName(); }
 
     @Override
-    public String glabel() { return op(); }
-
-    @Override
     StringBuilder _print1(StringBuilder sb) {
         in(1)._print0(sb.append("("));
         in(2)._print0(sb.append(op()));
diff --git a/chapter04/src/main/java/com/seaofnodes/simple/node/DivNode.java b/chapter04/src/main/java/com/seaofnodes/simple/node/DivNode.java
index 3b3a4436..c7276710 100644
--- a/chapter04/src/main/java/com/seaofnodes/simple/node/DivNode.java
+++ b/chapter04/src/main/java/com/seaofnodes/simple/node/DivNode.java
@@ -8,8 +8,6 @@ public class DivNode extends Node {
 
     @Override public String label() { return "Div"; }
 
-    @Override public String glabel() { return "//"; }
-
     @Override
     StringBuilder _print1(StringBuilder sb) {
         in(1)._print0(sb.append("("));
diff --git a/chapter04/src/main/java/com/seaofnodes/simple/node/MinusNode.java b/chapter04/src/main/java/com/seaofnodes/simple/node/MinusNode.java
index 0d59ef25..b83c41a5 100644
--- a/chapter04/src/main/java/com/seaofnodes/simple/node/MinusNode.java
+++ b/chapter04/src/main/java/com/seaofnodes/simple/node/MinusNode.java
@@ -8,8 +8,6 @@ public class MinusNode extends Node {
 
     @Override public String label() { return "Minus"; }
 
-    @Override public String glabel() { return "-"; }
-
     @Override
     StringBuilder _print1(StringBuilder sb) {
         in(1)._print0(sb.append("(-"));
diff --git a/chapter04/src/main/java/com/seaofnodes/simple/node/MulNode.java b/chapter04/src/main/java/com/seaofnodes/simple/node/MulNode.java
index 36d5eb3e..68ba9025 100644
--- a/chapter04/src/main/java/com/seaofnodes/simple/node/MulNode.java
+++ b/chapter04/src/main/java/com/seaofnodes/simple/node/MulNode.java
@@ -8,8 +8,6 @@ public class MulNode extends Node {
 
     @Override public String label() { return "Mul"; }
 
-    @Override public String glabel() { return "*"; }
-
     @Override
     StringBuilder _print1(StringBuilder sb) {
         in(1)._print0(sb.append("("));
diff --git a/chapter04/src/main/java/com/seaofnodes/simple/node/Node.java b/chapter04/src/main/java/com/seaofnodes/simple/node/Node.java
index 58516151..eb7d8333 100644
--- a/chapter04/src/main/java/com/seaofnodes/simple/node/Node.java
+++ b/chapter04/src/main/java/com/seaofnodes/simple/node/Node.java
@@ -67,13 +67,9 @@ public abstract class Node {
     // Easy reading label for debugger, e.g. "Add" or "Region" or "EQ"
     public abstract String label();
 
-    // Unique label for graph visualization, e.g. "Add12" or "Region30" or "EQ99"
+    // Unique label for debugging, e.g. "Add12" or "Region30" or "EQ99"
     public String uniqueName() { return label() + _nid; }
 
-    // Graphical label, e.g. "+" or "Region" or "=="
-    public String glabel() { return label(); }
-
-
     // ------------------------------------------------------------------------
 
     // Debugger Printing.
diff --git a/chapter04/src/main/java/com/seaofnodes/simple/node/NotNode.java b/chapter04/src/main/java/com/seaofnodes/simple/node/NotNode.java
index e3683646..83c63244 100644
--- a/chapter04/src/main/java/com/seaofnodes/simple/node/NotNode.java
+++ b/chapter04/src/main/java/com/seaofnodes/simple/node/NotNode.java
@@ -8,8 +8,6 @@ public class NotNode extends Node {
 
     @Override public String label() { return "Not"; }
 
-    @Override public String glabel() { return "!"; }
-
     @Override
     StringBuilder _print1(StringBuilder sb) {
         in(1)._print0(sb.append("(!"));
diff --git a/chapter04/src/main/java/com/seaofnodes/simple/node/SubNode.java b/chapter04/src/main/java/com/seaofnodes/simple/node/SubNode.java
index 58d757ea..c12e7388 100644
--- a/chapter04/src/main/java/com/seaofnodes/simple/node/SubNode.java
+++ b/chapter04/src/main/java/com/seaofnodes/simple/node/SubNode.java
@@ -8,8 +8,6 @@ public class SubNode extends Node {
 
     @Override public String label() { return "Sub"; }
 
-    @Override public String glabel() { return "-"; }
-
     @Override
     StringBuilder _print1(StringBuilder sb) {
         in(1)._print0(sb.append("("));
diff --git a/chapter04/src/main/java/com/seaofnodes/simple/print/JSViewer.java b/chapter04/src/main/java/com/seaofnodes/simple/print/JSViewer.java
deleted file mode 100644
index 43b0be2f..00000000
--- a/chapter04/src/main/java/com/seaofnodes/simple/print/JSViewer.java
+++ /dev/null
@@ -1,26 +0,0 @@
-package com.seaofnodes.simple.print;
-
-import com.seaofnodes.graph.*;
-import com.seaofnodes.simple.Parser;
-import java.io.IOException;
-
-public class JSViewer extends GraphViewer {
-    public static void main(String[] args) throws IOException {
-        try( var view = new JSViewer() ) { view.run(); }
-    }
-    JSViewer() throws IOException {}
-
-    @Override protected void compile(String src) {
-        Parser parser = new Parser(src);
-        parser._obs = new SimpleGraphObserver(parser) {
-            @Override protected void frame(GraphSnapshot snap, int pos, GraphEvent evt) throws IOException {
-                JSViewer.this.frame(snap, pos, evt);
-            }
-        };
-        try {
-            parser.parse();
-        } finally {
-            parser._obs = null;
-        }
-    }
-}
diff --git a/chapter04/src/main/java/com/seaofnodes/simple/print/SimpleGraphAdapter.java b/chapter04/src/main/java/com/seaofnodes/simple/print/SimpleGraphAdapter.java
index 72a11a87..a0ad7be0 100644
--- a/chapter04/src/main/java/com/seaofnodes/simple/print/SimpleGraphAdapter.java
+++ b/chapter04/src/main/java/com/seaofnodes/simple/print/SimpleGraphAdapter.java
@@ -17,7 +17,7 @@ public class SimpleGraphAdapter extends GraphAdapter<Node> {
     @Override protected Node out(Node n, int idx) { return n.out(idx); }
 
     private ArrayList<Edge> edges(Node n) {
-        String[] names = n instanceof ScopeNode scope ? scope.reverseNames() : null;
+        String[] names = n instanceof ScopeNode scope && n.nIns() != 0 ? scope.reverseNames() : null;
         var edges = new ArrayList<Edge>();
         for( int i = 0; i < n.nIns(); i++ ) {
             Role role = n instanceof ScopeNode || n instanceof ConstantNode ? Role.ASSOC
diff --git a/chapter04/src/main/java/com/seaofnodes/simple/print/SimpleGraphObserver.java b/chapter04/src/main/java/com/seaofnodes/simple/print/SimpleGraphObserver.java
index 865d1e20..f2ca7888 100644
--- a/chapter04/src/main/java/com/seaofnodes/simple/print/SimpleGraphObserver.java
+++ b/chapter04/src/main/java/com/seaofnodes/simple/print/SimpleGraphObserver.java
@@ -1,20 +1,36 @@
 package com.seaofnodes.simple.print;
 
 import com.seaofnodes.graph.GraphCapture;
+import com.seaofnodes.graph.GraphViewer;
 import com.seaofnodes.simple.Parser;
 import com.seaofnodes.simple.node.Node;
 import java.util.ArrayList;
+import java.io.IOException;
 
 /** Chapter 4 needs only a parser; it has no worklist or distant dependencies. */
-public abstract class SimpleGraphObserver extends GraphCapture<Node> {
-    private final Parser _parser;
-    protected SimpleGraphObserver(Parser parser) { super(new SimpleGraphAdapter()); _parser = parser; }
+public class SimpleGraphObserver extends GraphCapture<Node> {
+    private Parser _parser;
+    private Node _ret;
+    public SimpleGraphObserver() { super(new SimpleGraphAdapter()); }
+    public static void main(String[] args) throws IOException {
+        GraphViewer.run(new SimpleGraphObserver());
+    }
+    @Override protected void compile(String src) {
+        _parser = new Parser(src);
+        _parser._obs = this;
+        _ret = _parser.parse();
+        phase("Parse");
+    }
     @Override protected String phase() { return "Parse"; }
     @Override protected int pos() { return _parser.pos(); }
-    @Override protected void detach() { _parser._obs = null; }
+    @Override protected void detach() {
+        if( _parser != null ) _parser._obs = null;
+        _parser = null;
+        _ret = null;
+    }
     @Override protected void roots(ArrayList<Node> roots) {
         roots.add(Parser.START);
         roots.add(_parser._scope);
-        roots.add(_parser._ret);
+        roots.add(_ret);
     }
 }
diff --git a/chapter04/src/test/java/com/seaofnodes/simple/Chapter02Test.java b/chapter04/src/test/java/com/seaofnodes/simple/Chapter02Test.java
index 60ee8874..9de09d21 100644
--- a/chapter04/src/test/java/com/seaofnodes/simple/Chapter02Test.java
+++ b/chapter04/src/test/java/com/seaofnodes/simple/Chapter02Test.java
@@ -14,8 +14,6 @@ public class Chapter02Test {
         Node._disablePeephole = true; // disable peephole so we can observe full graph
         ReturnNode ret = parser.parse();
         assertEquals("return (1+((2*3)+(-5)));", ret.print());
-        GraphVisualizer gv = new GraphVisualizer();
-        System.out.println(gv.generateDotOutput(parser));
         Node._disablePeephole = false;
     }
 
@@ -59,8 +57,6 @@ public class Chapter02Test {
         Parser parser = new Parser("return 1+2*3+-5;");
         ReturnNode ret = parser.parse();
         assertEquals("return 2;", ret.print());
-        GraphVisualizer gv = new GraphVisualizer();
-        System.out.println(gv.generateDotOutput(parser));
     }
 
 }
diff --git a/chapter04/src/test/java/com/seaofnodes/simple/Chapter03Test.java b/chapter04/src/test/java/com/seaofnodes/simple/Chapter03Test.java
index fc8e97b6..6a5d7072 100644
--- a/chapter04/src/test/java/com/seaofnodes/simple/Chapter03Test.java
+++ b/chapter04/src/test/java/com/seaofnodes/simple/Chapter03Test.java
@@ -31,7 +31,7 @@ public class Chapter03Test {
 
     @Test
     public void testVarScopeNoPeephole() {
-        Parser parser = new Parser("int a=1; int b=2; int c=0; { int b=3; c=a+b; #showGraph; } return c; #showGraph;");
+        Parser parser = new Parser("int a=1; int b=2; int c=0; { int b=3; c=a+b;  } return c; ");
         Node._disablePeephole = true;
         ReturnNode ret = parser.parse();
         Node._disablePeephole = false;
@@ -40,7 +40,7 @@ public class Chapter03Test {
 
     @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); #showGraph;");
+        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());
     }
diff --git a/chapter04/src/test/java/com/seaofnodes/simple/Chapter04Test.java b/chapter04/src/test/java/com/seaofnodes/simple/Chapter04Test.java
index faae0aee..28912d5d 100644
--- a/chapter04/src/test/java/com/seaofnodes/simple/Chapter04Test.java
+++ b/chapter04/src/test/java/com/seaofnodes/simple/Chapter04Test.java
@@ -10,7 +10,7 @@ public class Chapter04Test {
 
     @Test
     public void testPeephole() {
-        Parser parser = new Parser("return 1+arg+2; #showGraph;");
+        Parser parser = new Parser("return 1+arg+2; ");
         ReturnNode ret = parser.parse();
         assertEquals("return (arg+3);", ret.print());
     }
@@ -38,7 +38,7 @@ public class Chapter04Test {
 
     @Test
     public void testPeephole3() {
-        Parser parser = new Parser("return 1+arg+2+arg+3; #showGraph;");
+        Parser parser = new Parser("return 1+arg+2+arg+3; ");
         ReturnNode ret = parser.parse();
         assertEquals("return ((arg*2)+6);", ret.print());
     }
@@ -52,7 +52,7 @@ public class Chapter04Test {
 
     @Test
     public void testVarArg() {
-        Parser parser = new Parser("return arg; #showGraph;", TypeInteger.BOT);
+        Parser parser = new Parser("return arg; ", TypeInteger.BOT);
         ReturnNode ret = parser.parse();
         assertTrue(ret.in(0) instanceof ProjNode);
         assertTrue(ret.in(1) instanceof ProjNode);
@@ -60,49 +60,49 @@ public class Chapter04Test {
 
     @Test
     public void testConstantArg() {
-        Parser parser = new Parser("return arg; #showGraph;", TypeInteger.constant(2));
+        Parser parser = new Parser("return arg; ", TypeInteger.constant(2));
         ReturnNode ret = parser.parse();
         assertEquals("return 2;", ret.print());
     }
 
     @Test
     public void testCompEq() {
-        Parser parser = new Parser("return 3==3; #showGraph;");
+        Parser parser = new Parser("return 3==3; ");
         ReturnNode ret = parser.parse();
         assertEquals("return 1;", ret.print());
     }
 
     @Test
     public void testCompEq2() {
-        Parser parser = new Parser("return 3==4; #showGraph;");
+        Parser parser = new Parser("return 3==4; ");
         ReturnNode ret = parser.parse();
         assertEquals("return 0;", ret.print());
     }
 
     @Test
     public void testCompNEq() {
-        Parser parser = new Parser("return 3!=3; #showGraph;");
+        Parser parser = new Parser("return 3!=3; ");
         ReturnNode ret = parser.parse();
         assertEquals("return 0;", ret.print());
     }
 
     @Test
     public void testCompNEq2() {
-        Parser parser = new Parser("return 3!=4; #showGraph;");
+        Parser parser = new Parser("return 3!=4; ");
         ReturnNode ret = parser.parse();
         assertEquals("return 1;", ret.print());
     }
 
     @Test
     public void testBug1() {
-        Parser parser = new Parser("int a=arg+1; int b=a; b=1; return a+2; #showGraph;");
+        Parser parser = new Parser("int a=arg+1; int b=a; b=1; return a+2; ");
         ReturnNode ret = parser.parse();
         assertEquals("return (arg+3);", ret.print());
     }
 
     @Test
     public void testBug2() {
-        Parser parser = new Parser("int a=arg+1; a=a; return a; #showGraph;");
+        Parser parser = new Parser("int a=arg+1; a=a; return a; ");
         ReturnNode ret = parser.parse();
         assertEquals("return (arg+1);", ret.print());
     }