Move debug printing into shared space

Same as the graph viewer, moves a lot of code out of all Nodes

33 files changed, 148 insertions, 532 deletions

diff --git a/chapter12/src/main/java/com/seaofnodes/simple/IRPrinter.java b/chapter12/src/main/java/com/seaofnodes/simple/IRPrinter.java
index 3410ab64..7e93e9da 100644
--- a/chapter12/src/main/java/com/seaofnodes/simple/IRPrinter.java
+++ b/chapter12/src/main/java/com/seaofnodes/simple/IRPrinter.java
@@ -1,288 +1,33 @@
 package com.seaofnodes.simple;
 
+import com.seaofnodes.print.IRAdapter;
 import com.seaofnodes.simple.node.*;
-import java.lang.StringBuilder;
-import java.util.ArrayList;
-import java.util.BitSet;
-import java.util.HashMap;
-import java.util.IdentityHashMap;
-
-public class IRPrinter {
-
-    // Print a node on 1 line, columnar aligned, as:
-    // NNID NNAME DDEF DDEF  [[  UUSE UUSE  ]]  TYPE
-    // 1234 sssss 1234 1234 1234 1234 1234 1234 tttttt
-    public static void _printLine( Node n, StringBuilder sb ) {
-        sb.append("%4d %-7.7s ".formatted(n._nid,n.label()));
-        if( n.isDead() ) {
-            sb.append("DEAD\n");
-            return;
-        }
-        for( Node def : n._inputs )
-            sb.append(def==null ? "____ " : "%4d ".formatted(def._nid));
-        for( int i = n._inputs.size(); i<4; i++ )
-            sb.append("     ");
-        sb.append(" [[  ");
-        for( Node use : n._outputs )
-            sb.append(use==null ? "____ " : "%4d ".formatted(use._nid));
-        int lim = 6 - Math.max(n._inputs.size(),4);
-        for( int i = n._outputs.size(); i<lim; i++ )
-            sb.append("     ");
-        sb.append(" ]]  ");
-        if( n._type!= null ) sb.append(n._type.str());
-        sb.append("\n");
-    }
-
-    private static StringBuilder nodeId(StringBuilder sb, Node n) {
-        sb.append("%%%d".formatted(n._nid));
-        if (n instanceof ProjNode proj) {
-            sb.append(".").append(proj._idx);
-        }
-        return sb;
-    }
-
-    // Print a node on 1 line, format is inspired by LLVM
-    // %id: TYPE = NODE(inputs ....)
-    // Nodes as referred to as %id
-    public static void _printLineLlvmFormat( Node n, StringBuilder sb ) {
-        nodeId(sb, n).append(": ");
-        if( n.isDead() ) {
-            sb.append("DEAD\n");
-            return;
-        }
-        if( n._type!= null ) n._type.typeName(sb);
-        sb.append(" = ").append( n.label() ).append( "(" );
-        for( int i = 0; i < n._inputs.size(); i++ ) {
-            Node def = n.in(i);
-            if (i > 0)
-                sb.append(", ");
-            if (def == null) sb.append("_");
-            else             nodeId(sb, def);
-        }
-        sb.append(")").append("\n");
-    }
-
-    public static void printLine( Node n, StringBuilder sb, boolean llvmFormat ) {
-        if (llvmFormat) _printLineLlvmFormat( n, sb );
-        else            _printLine          ( n, sb );
-    }
-
-    public static String prettyPrint(Node node, int depth) {
-        return Parser.SCHEDULED
-            ? prettyPrintScheduled( node, depth, false )
-            : prettyPrint( node, depth, false );
-    }
-
-    // Another bulk pretty-printer.  Makes more effort at basic-block grouping.
-    public static String prettyPrint( Node node, int depth, boolean llvmFormat ) {
-        // First, a Breadth First Search at a fixed depth.
-        BFS bfs = new BFS(node,depth);
-        // Convert just that set to a post-order
-        ArrayList<Node> rpos = new ArrayList<>();
-        BitSet visit = new BitSet();
-        for( int i=bfs._lim; i< bfs._bfs.size(); i++ )
-            postOrd( bfs._bfs.get(i), rpos, visit, bfs._bs);
-        // Reverse the post-order walk
-        StringBuilder sb = new StringBuilder();
-        boolean gap=false;
-        for( int i=rpos.size()-1; i>=0; i-- ) {
-            Node n = rpos.get(i);
-            if( n.isCFG() || n.isMultiHead() ) {
-                if( !gap ) sb.append("\n"); // Blank before multihead
-                printLine( n, sb, llvmFormat ); // Print head
-                while( --i >= 0 ) {
-                    Node t = rpos.get(i);
-                    if( !t.isMultiTail() ) { i++; break; }
-                    printLine( t, sb, llvmFormat );
-                }
-                sb.append("\n"); // Blank after multitail
-                gap = true;
-            } else {
-                printLine( n, sb, llvmFormat );
-                gap = false;
-            }
-        }
-        return sb.toString();
-    }
-
-    private static void postOrd(Node n, ArrayList<Node> rpos, BitSet visit, BitSet bfs) {
-        if( !bfs.get(n._nid) )
-            return;  // Not in the BFS visit
-        if( visit.get(n._nid) ) return; // Already post-order walked
-        visit.set(n._nid);
-        // First walk the CFG, then everything
-        if( n.isCFG() ) {
-            for( Node use : n._outputs )
-                if( use!=null && use.isCFG() && use.nOuts()>=1 && !(use._outputs.get(0) instanceof LoopNode) )
-                    postOrd(use, rpos,visit,bfs);
-            for( Node use : n._outputs )
-                if( use!=null && use.isCFG() )
-                    postOrd(use,rpos,visit,bfs);
-        }
-        for( Node use : n._outputs )
-            if( use != null )
-                postOrd(use, rpos,visit,bfs);
-        // Post-order
-        rpos.add(n);
-    }
-
-    // Breadth-first search, broken out in a class to keep in more independent.
-    // Maintains a root-set of Nodes at the limit (or past by 1 if MultiHead).
-    public static class BFS {
-        // A breadth first search, plus MultiHeads for any MultiTails
-        public final ArrayList<Node> _bfs;
-        public final BitSet _bs; // Visited members by node id
-        public final int _depth; // Depth limit
-        public final int _lim; // From here to _bfs._len can be roots for a reverse search
-        public BFS( Node base, int d ) {
-            _depth = d;
-            _bfs = new ArrayList<>();
-            _bs = new BitSet();
-
-            add(base);                 // Prime the pump
-            int idx=0, lim=1;          // Limit is where depth counter changes
-            while( idx < _bfs.size() ) { // Ran out of nodes below depth
-                Node n = _bfs.get(idx++);
-                for( Node def : n._inputs )
-                    if( def!=null && !_bs.get(def._nid) )
-                        add(def);
-                if( idx==lim ) {    // Depth counter changes at limit
-                    if( --d < 0 )
-                        break;      // Ran out of depth
-                    lim = _bfs.size();  // New depth limit
-                }
-            }
-            // Toss things past the limit except multi-heads
-            while( idx < _bfs.size() ) {
-                Node n = _bfs.get(idx);
-                if( n.isMultiHead() ) idx++;
-                else del(idx);
-            }
-            // Root set is any node with no inputs in the visited set
-            lim = _bfs.size();
-            for( int i=_bfs.size()-1; i>=0; i-- )
-                if( !any_visited(_bfs.get(i)) )
-                    swap( i,--lim);
-            _lim = lim;
-        }
-        void swap( int x, int y ) {
-            if( x==y ) return;
-            Node tx = _bfs.get(x);
-            Node ty = _bfs.get(y);
-            _bfs.set(x,ty);
-            _bfs.set(y,tx);
-        }
-        void add(Node n) {
-            _bfs.add(n);
-            _bs.set(n._nid);
-        }
-        void del(int idx) {
-            Node n = Utils.del(_bfs, idx);
-            _bs.clear(n._nid);
-        }
-        boolean any_visited( Node n ) {
-            for( Node def : n._inputs )
-                if( def!=null && _bs.get(def._nid) )
-                    return true;
-            return false;
-        }
-    }
-
-    // Diagnostic block ordering from raw control edges.  Do not call idepth():
-    // it fills compiler caches (and can walk lazy dominator accessors).
-    private static int _idepth(CFGNode cfg, HashMap<Integer,Integer> depths) {
-        if( cfg == null || cfg instanceof StartNode ) return 0;
-        Integer old = depths.get(cfg._nid);
-        if( old != null ) return old;
-        depths.put(cfg._nid,0); // Break cycles in partially constructed graphs.
-        int d = 0;
-        if( cfg instanceof LoopNode ) {
-            d = _idepth((CFGNode)cfg.in(1),depths)+1;
-        } else if( cfg instanceof RegionNode || cfg instanceof StopNode ) {
-            for( Node n : cfg._inputs )
-                if( n instanceof CFGNode pred ) d = Math.max(d,_idepth(pred,depths)+1);
-        } else if( cfg.in(0) instanceof CFGNode pred ) {
-            d = _idepth(pred,depths)+1;
-        }
-        depths.put(cfg._nid,d);
-        return d;
-    }
-
-    // Bulk pretty printer, knowing scheduling information is available
-    public static String prettyPrintScheduled( Node node, int depth, boolean llvmFormat ) {
-        // Backwards DFS walk to depth.
-        IdentityHashMap<Node,Integer> ds = new IdentityHashMap<>();
-        _walk(ds,node,depth);
-        // Print by block with least diagnostic depth
-        HashMap<Integer,Integer> depths = new HashMap<>();
-        StringBuilder sb = new StringBuilder();
-        ArrayList<Node> bns = new ArrayList<>();
-        while( !ds.isEmpty() ) {
-            CFGNode blk = null;
-            for( Node n : ds.keySet() ) {
-                CFGNode cfg = n instanceof CFGNode cfg0 && cfg0.blockHead() ? cfg0 : (CFGNode)n.in(0);
-                if( blk==null || _idepth(cfg,depths) < _idepth(blk,depths) )
-                    blk = cfg;
-            }
-            ds.remove(blk);
-
-            // Print block header
-            sb.append("%-13.13s".formatted(label(blk)+":"));
-            sb.append( "     ".repeat(4) ).append(" [[  ");
-            if( blk instanceof RegionNode || blk instanceof StopNode )
-                for( int i=(blk instanceof StopNode ? 0 : 1); i<blk.nIns(); i++ )
-                    label(sb,blk.cfg(i));
-            else if( !(blk instanceof StartNode) )
-                label(sb,blk.cfg(0));
-            sb.append(" ]]  \n");
-
-            // Collect block contents that are in the depth limit
-            bns.clear();
-            int xd = Integer.MAX_VALUE;
-            for( Node use : blk._outputs ) {
-                Integer i = ds.get(use);
-                if( i!=null && !(use instanceof CFGNode cfg && cfg.blockHead()) ) {
-                    bns.add(use);
-                    xd = Math.min(xd,i);
-                }
-            }
-            // Print Phis up front, if any
-            for( int i=0; i<bns.size(); i++ )
-                if( bns.get(i) instanceof PhiNode phi )
-                    printLine( phi, sb, llvmFormat,bns,i--,ds);
-
-            // Print block contents in depth order, bumping depth until whole block printed
-            for( ; !bns.isEmpty(); xd++ )
-                for( int i=0; i<bns.size(); i++ )
-                    if( ds.get(bns.get(i))==xd )
-                        printLine( bns.get(i), sb, llvmFormat, bns, i--, ds );
-            sb.append("\n");
-        }
-        return sb.toString();
-    }
-
-    private static void _walk( IdentityHashMap<Node,Integer> ds, Node node, int d ) {
-        Integer nd = ds.get(node);
-        if( nd!=null && d <= nd ) return; // Been there, done that
-        ds.put(node,d);
-        if( d == 0 ) return;    // Depth cutoff
-        for( Node def : node._inputs )
-            if( def != null )
-                _walk(ds,def,d-1);
-    }
-
-    static String label( CFGNode blk ) {
-        if( blk instanceof StartNode ) return "START";
-        return (blk instanceof LoopNode ? "LOOP" : "L")+blk._nid;
-    }
-    static void label( StringBuilder sb, CFGNode blk ) {
-        if( !blk.blockHead() ) blk = blk.cfg(0);
-        sb.append( "%-9.9s ".formatted( label( blk ) ) );
-    }
-    static void printLine( Node n, StringBuilder sb, boolean llvmFormat, ArrayList<Node> bns, int i, IdentityHashMap<Node,Integer> ds ) {
-        printLine( n, sb, llvmFormat );
-        Utils.del(bns,i);
-        ds.remove(n);
-    }
 
+/** This chapter's read-only IR facts and the familiar debugger entry points. */
+public final class IRPrinter extends IRAdapter<Node> {
+    private static final com.seaofnodes.print.IRPrinter<Node> PRINT =
+        new com.seaofnodes.print.IRPrinter<>(new IRPrinter());
+    @Override public String type(Node n) { return n._type==null ? "" : n._type.str(); }
+    @Override public String inputMark(Node n, Node def) { return n instanceof MemMergeNode && def instanceof MemMergeNode ? "^" : " "; }
+    @Override public Kind kind(Node n) {
+        if( n instanceof StartNode ) return Kind.START;
+        if( n instanceof StopNode ) return Kind.STOP;
+        if( n instanceof LoopNode ) return Kind.LOOP;
+        if( n instanceof RegionNode ) return Kind.REGION;
+        if( n instanceof PhiNode ) return Kind.PHI;
+        if( n instanceof ReturnNode ) return Kind.RETURN;
+        if( n instanceof ConstantNode ) return Kind.CONSTANT;
+        if( n instanceof CProjNode ) return Kind.CPROJ;
+        if( n instanceof ProjNode ) return n instanceof CFGNode ? Kind.CPROJ : Kind.PROJ;
+        if( n instanceof CFGNode ) return Kind.CTRL;
+        if( n instanceof MultiNode ) return Kind.MULTI;
+        return Kind.DATA;
+    }
+    @Override public int index(Node n) {
+        if( n instanceof ProjNode p ) return p._idx;
+        if( n instanceof CProjNode p ) return p._idx;
+        return n._nid;
+    }
+
+    public static String prettyPrint(Node n, int depth) { return PRINT.prettyPrint(n,depth); }
 }
diff --git a/chapter12/src/main/java/com/seaofnodes/simple/node/AddFNode.java b/chapter12/src/main/java/com/seaofnodes/simple/node/AddFNode.java
index 5d0a473a..fd713156 100644
--- a/chapter12/src/main/java/com/seaofnodes/simple/node/AddFNode.java
+++ b/chapter12/src/main/java/com/seaofnodes/simple/node/AddFNode.java
@@ -1,21 +1,16 @@
 package com.seaofnodes.simple.node;
 
+
 import com.seaofnodes.simple.type.Type;
 import com.seaofnodes.simple.type.TypeFloat;
 
-import java.util.BitSet;
 
 public class AddFNode extends Node {
     public AddFNode(Node lhs, Node rhs) { super(null, lhs, rhs); }
 
     @Override public String label() { return "AddF"; }
 
-    @Override
-    StringBuilder _print1(StringBuilder sb, BitSet visited) {
-        in(1)._print0(sb.append("("), visited);
-        in(2)._print0(sb.append("+"), visited);
-        return sb.append(")");
-    }
+    @Override protected String format() { return "(%1+%2)"; }
 
     @Override
     public Type compute() {
diff --git a/chapter12/src/main/java/com/seaofnodes/simple/node/AddNode.java b/chapter12/src/main/java/com/seaofnodes/simple/node/AddNode.java
index 188c50a8..01aa209f 100644
--- a/chapter12/src/main/java/com/seaofnodes/simple/node/AddNode.java
+++ b/chapter12/src/main/java/com/seaofnodes/simple/node/AddNode.java
@@ -1,20 +1,15 @@
 package com.seaofnodes.simple.node;
 
+
 import com.seaofnodes.simple.type.*;
 
-import java.util.BitSet;
 
 public class AddNode extends Node {
     public AddNode(Node lhs, Node rhs) { super(null, lhs, rhs); }
 
     @Override public String label() { return "Add"; }
 
-    @Override
-    StringBuilder _print1(StringBuilder sb, BitSet visited) {
-        in(1)._print0(sb.append("("), visited);
-        in(2)._print0(sb.append("+"), visited);
-        return sb.append(")");
-    }
+    @Override protected String format() { return "(%1+%2)"; }
 
 
     @Override
diff --git a/chapter12/src/main/java/com/seaofnodes/simple/node/BoolNode.java b/chapter12/src/main/java/com/seaofnodes/simple/node/BoolNode.java
index 2055ea6f..e515a5f1 100644
--- a/chapter12/src/main/java/com/seaofnodes/simple/node/BoolNode.java
+++ b/chapter12/src/main/java/com/seaofnodes/simple/node/BoolNode.java
@@ -1,5 +1,7 @@
 package com.seaofnodes.simple.node;
 
+import com.seaofnodes.print.ExprPrinter;
+
 import com.seaofnodes.simple.Parser;
 import com.seaofnodes.simple.Utils;
 import com.seaofnodes.simple.type.Type;
@@ -7,7 +9,6 @@ import com.seaofnodes.simple.type.TypeInteger;
 import com.seaofnodes.simple.type.TypeFloat;
 import com.seaofnodes.simple.type.TypeMemPtr;
 
-import java.util.BitSet;
 
 abstract public class BoolNode extends Node {
 
@@ -20,11 +21,8 @@ abstract public class BoolNode extends Node {
     @Override
     public String label() { return getClass().getSimpleName(); }
 
-    @Override
-    StringBuilder _print1(StringBuilder sb, BitSet visited) {
-        in(1)._print0(sb.append("("), visited);
-        in(2)._print0(sb.append(op()), visited);
-        return sb.append(")");
+    @Override protected ExprPrinter<Node> _print1(ExprPrinter<Node> p) {
+        return p.open().n(in(1)).p(op()).n(in(2)).close();
     }
 
     @Override
diff --git a/chapter12/src/main/java/com/seaofnodes/simple/node/CProjNode.java b/chapter12/src/main/java/com/seaofnodes/simple/node/CProjNode.java
index fb0ff879..ff5d1a76 100644
--- a/chapter12/src/main/java/com/seaofnodes/simple/node/CProjNode.java
+++ b/chapter12/src/main/java/com/seaofnodes/simple/node/CProjNode.java
@@ -1,10 +1,11 @@
 package com.seaofnodes.simple.node;
 
+import com.seaofnodes.print.ExprPrinter;
+
 import com.seaofnodes.simple.Parser;
 import com.seaofnodes.simple.type.Type;
 import com.seaofnodes.simple.type.TypeMem;
 import com.seaofnodes.simple.type.TypeTuple;
-import java.util.BitSet;
 
 public class CProjNode extends CFGNode {
 
@@ -22,7 +23,7 @@ public class CProjNode extends CFGNode {
 
     @Override public String label() { return _label; }
 
-    @Override StringBuilder _print1(StringBuilder sb, BitSet visited) { return sb.append(_label); }
+    @Override protected ExprPrinter<Node> _print1(ExprPrinter<Node> p) { return p.p(_label); }
 
     @Override public boolean isMultiTail() { return in(0).isMultiHead(); }
     @Override public boolean blockHead() { return true; }
diff --git a/chapter12/src/main/java/com/seaofnodes/simple/node/CastNode.java b/chapter12/src/main/java/com/seaofnodes/simple/node/CastNode.java
index fec540f7..c1faf210 100644
--- a/chapter12/src/main/java/com/seaofnodes/simple/node/CastNode.java
+++ b/chapter12/src/main/java/com/seaofnodes/simple/node/CastNode.java
@@ -1,10 +1,11 @@
 package com.seaofnodes.simple.node;
 
+import com.seaofnodes.print.ExprPrinter;
+
 import com.seaofnodes.simple.type.Type;
 import com.seaofnodes.simple.type.TypeInteger;
 import com.seaofnodes.simple.IterPeeps;
 
-import java.util.BitSet;
 
 // Upcast (join) the input to a t.  Used after guard test to lift an input.
 // Can also be used to make a type-assertion if ctrl is null.
@@ -18,12 +19,9 @@ public class CastNode extends Node {
 
     @Override public String label() { return "("+_t.str()+")"; }
 
-    @Override
-    public String uniqueName() { return "Cast_" + _nid; }
 
-    @Override
-    StringBuilder _print1(StringBuilder sb, BitSet visited) {
-        return in(1)._print0(sb.append(label()), visited);
+    @Override protected ExprPrinter<Node> _print1(ExprPrinter<Node> p) {
+        return p.p(label()).n(in(1));
     }
 
     @Override
diff --git a/chapter12/src/main/java/com/seaofnodes/simple/node/ConstantNode.java b/chapter12/src/main/java/com/seaofnodes/simple/node/ConstantNode.java
index 37a529d1..9ecd1152 100644
--- a/chapter12/src/main/java/com/seaofnodes/simple/node/ConstantNode.java
+++ b/chapter12/src/main/java/com/seaofnodes/simple/node/ConstantNode.java
@@ -1,9 +1,10 @@
 package com.seaofnodes.simple.node;
 
+import com.seaofnodes.print.ExprPrinter;
+
 import com.seaofnodes.simple.Parser;
 import com.seaofnodes.simple.type.Type;
 
-import java.util.BitSet;
 
 /**
  * A Constant node represents a constant value.  At present, the only constants
@@ -24,15 +25,16 @@ public class ConstantNode extends Node {
         _con = type;
     }
 
-    @Override
-    public String label() { return "#"+_con; }
+    @Override protected String repeatName() {
+        return _con==null || _con.toString().length()<=32 ? null : uniqueName();
+    }
 
     @Override
-    public String uniqueName() { return "Con_" + _nid; }
+    public String label() { return "Con"; }
 
-    @Override
-    StringBuilder _print1(StringBuilder sb, BitSet visited) {
-        return _con.print(sb);
+
+    @Override protected ExprPrinter<Node> _print1(ExprPrinter<Node> p) {
+        return p.p(_con);
     }
 
     @Override public boolean isMultiTail() { return true; }
diff --git a/chapter12/src/main/java/com/seaofnodes/simple/node/DivFNode.java b/chapter12/src/main/java/com/seaofnodes/simple/node/DivFNode.java
index 6c0c2eb3..a3f4318d 100644
--- a/chapter12/src/main/java/com/seaofnodes/simple/node/DivFNode.java
+++ b/chapter12/src/main/java/com/seaofnodes/simple/node/DivFNode.java
@@ -1,21 +1,16 @@
 package com.seaofnodes.simple.node;
 
+
 import com.seaofnodes.simple.type.Type;
 import com.seaofnodes.simple.type.TypeFloat;
 
-import java.util.BitSet;
 
 public class DivFNode extends Node {
     public DivFNode(Node lhs, Node rhs) { super(null, lhs, rhs); }
 
     @Override public String label() { return "DivF"; }
 
-    @Override
-    StringBuilder _print1(StringBuilder sb, BitSet visited) {
-        in(1)._print0(sb.append("("), visited);
-        in(2)._print0(sb.append("/"), visited);
-        return sb.append(")");
-    }
+    @Override protected String format() { return "(%1/%2)"; }
 
     @Override
     public Type compute() {
diff --git a/chapter12/src/main/java/com/seaofnodes/simple/node/DivNode.java b/chapter12/src/main/java/com/seaofnodes/simple/node/DivNode.java
index bc9ff7d9..cd52d117 100644
--- a/chapter12/src/main/java/com/seaofnodes/simple/node/DivNode.java
+++ b/chapter12/src/main/java/com/seaofnodes/simple/node/DivNode.java
@@ -1,21 +1,16 @@
 package com.seaofnodes.simple.node;
 
+
 import com.seaofnodes.simple.type.Type;
 import com.seaofnodes.simple.type.TypeInteger;
 
-import java.util.BitSet;
 
 public class DivNode extends Node {
     public DivNode(Node lhs, Node rhs) { super(null, lhs, rhs); }
 
     @Override public String label() { return "Div"; }
 
-    @Override
-    StringBuilder _print1(StringBuilder sb, BitSet visited) {
-        in(1)._print0(sb.append("("), visited);
-        in(2)._print0(sb.append("/"), visited);
-        return sb.append(")");
-    }
+    @Override protected String format() { return "(%1/%2)"; }
 
     @Override
     public Type compute() {
diff --git a/chapter12/src/main/java/com/seaofnodes/simple/node/IfNode.java b/chapter12/src/main/java/com/seaofnodes/simple/node/IfNode.java
index 5457ac6e..70340f7f 100644
--- a/chapter12/src/main/java/com/seaofnodes/simple/node/IfNode.java
+++ b/chapter12/src/main/java/com/seaofnodes/simple/node/IfNode.java
@@ -1,5 +1,6 @@
 package com.seaofnodes.simple.node;
 
+
 import com.seaofnodes.simple.IterPeeps;
 import com.seaofnodes.simple.type.Type;
 import com.seaofnodes.simple.type.TypeInteger;
@@ -17,11 +18,7 @@ public class IfNode extends CFGNode implements MultiNode {
     @Override
     public String label() { return "If"; }
 
-    @Override
-    StringBuilder _print1(StringBuilder sb, BitSet visited) {
-        sb.append("if( ");
-        return in(1)._print0(sb, visited).append(" )");
-    }
+    @Override protected String format() { return "if( %1 )"; }
 
     @Override public boolean isMultiHead() { return true; }
 
diff --git a/chapter12/src/main/java/com/seaofnodes/simple/node/LoadNode.java b/chapter12/src/main/java/com/seaofnodes/simple/node/LoadNode.java
index 72af8101..01a82a79 100644
--- a/chapter12/src/main/java/com/seaofnodes/simple/node/LoadNode.java
+++ b/chapter12/src/main/java/com/seaofnodes/simple/node/LoadNode.java
@@ -1,11 +1,12 @@
 package com.seaofnodes.simple.node;
 
+import com.seaofnodes.print.ExprPrinter;
+
 import com.seaofnodes.simple.Utils;
 import com.seaofnodes.simple.IterPeeps;
 import com.seaofnodes.simple.type.Type;
 import com.seaofnodes.simple.type.Field;
 
-import java.util.BitSet;
 
 /**
  * Load represents extracting a value from inside a memory object,
@@ -48,7 +49,7 @@ public class LoadNode extends MemOpNode {
     public String label() { return "Load"; }
 
     @Override
-    StringBuilder _print1(StringBuilder sb, BitSet visited) { return sb.append(".").append(_name); }
+    protected ExprPrinter<Node> _print1(ExprPrinter<Node> p) { return p.p(".").p(_name); }
 
     @Override
     public Type compute() {
diff --git a/chapter12/src/main/java/com/seaofnodes/simple/node/MemMergeNode.java b/chapter12/src/main/java/com/seaofnodes/simple/node/MemMergeNode.java
index d7fed402..f3d5b01e 100644
--- a/chapter12/src/main/java/com/seaofnodes/simple/node/MemMergeNode.java
+++ b/chapter12/src/main/java/com/seaofnodes/simple/node/MemMergeNode.java
@@ -1,9 +1,10 @@
 package com.seaofnodes.simple.node;
 
+import com.seaofnodes.print.ExprPrinter;
+
 import com.seaofnodes.simple.IterPeeps;
 import com.seaofnodes.simple.type.Type;
 import com.seaofnodes.simple.type.TypeMem;
-import java.util.BitSet;
 
 /** All memory: a default slice and explicit overrides for individual aliases. */
 public class MemMergeNode extends Node {
@@ -28,14 +29,14 @@ public class MemMergeNode extends Node {
     @Override public String label() { return "MemMerge"; }
     @Override public boolean isMem() { return true; }
     @Override public Type compute() { return TypeMem.BOT; }
-    @Override StringBuilder _print1(StringBuilder sb, BitSet visited) {
-        sb.append("MEM[");
+    @Override protected ExprPrinter<Node> _print1(ExprPrinter<Node> p) {
+        p.p("MEM[");
         for( int i=1; i<nIns(); i++ )
             if( in(i)!=null ) {
-                sb.append(i==1 ? "default:" : i+":");
-                in(i)._print0(sb,visited).append(" ");
+                p.p(i==1 ? "default:" : i+":");
+                p.n(in(i)).p(" ");
             }
-        return sb.append("]");
+        return p.p("]");
     }
 
     @Override public Node idealize() {
diff --git a/chapter12/src/main/java/com/seaofnodes/simple/node/MinusFNode.java b/chapter12/src/main/java/com/seaofnodes/simple/node/MinusFNode.java
index 7cacf2c9..1b45c7c5 100644
--- a/chapter12/src/main/java/com/seaofnodes/simple/node/MinusFNode.java
+++ b/chapter12/src/main/java/com/seaofnodes/simple/node/MinusFNode.java
@@ -1,20 +1,16 @@
 package com.seaofnodes.simple.node;
 
+
 import com.seaofnodes.simple.type.Type;
 import com.seaofnodes.simple.type.TypeFloat;
 
-import java.util.BitSet;
 
 public class MinusFNode extends Node {
     public MinusFNode(Node in) { super(null, in); }
 
     @Override public String label() { return "MinusF"; }
 
-    @Override
-    StringBuilder _print1(StringBuilder sb, BitSet visited) {
-        in(1)._print0(sb.append("(-"), visited);
-        return sb.append(")");
-    }
+    @Override protected String format() { return "(-%1)"; }
 
     @Override
     public Type compute() {
diff --git a/chapter12/src/main/java/com/seaofnodes/simple/node/MinusNode.java b/chapter12/src/main/java/com/seaofnodes/simple/node/MinusNode.java
index c3be733c..ae450b22 100644
--- a/chapter12/src/main/java/com/seaofnodes/simple/node/MinusNode.java
+++ b/chapter12/src/main/java/com/seaofnodes/simple/node/MinusNode.java
@@ -1,20 +1,16 @@
 package com.seaofnodes.simple.node;
 
+
 import com.seaofnodes.simple.type.Type;
 import com.seaofnodes.simple.type.TypeInteger;
 
-import java.util.BitSet;
 
 public class MinusNode extends Node {
     public MinusNode(Node in) { super(null, in); }
 
     @Override public String label() { return "Minus"; }
 
-    @Override
-    StringBuilder _print1(StringBuilder sb, BitSet visited) {
-        in(1)._print0(sb.append("(-"), visited);
-        return sb.append(")");
-    }
+    @Override protected String format() { return "(-%1)"; }
 
     @Override
     public Type compute() {
diff --git a/chapter12/src/main/java/com/seaofnodes/simple/node/MulFNode.java b/chapter12/src/main/java/com/seaofnodes/simple/node/MulFNode.java
index 4b753ba7..6a57f3c5 100644
--- a/chapter12/src/main/java/com/seaofnodes/simple/node/MulFNode.java
+++ b/chapter12/src/main/java/com/seaofnodes/simple/node/MulFNode.java
@@ -1,21 +1,16 @@
 package com.seaofnodes.simple.node;
 
+
 import com.seaofnodes.simple.type.Type;
 import com.seaofnodes.simple.type.TypeFloat;
 
-import java.util.BitSet;
 
 public class MulFNode extends Node {
     public MulFNode(Node lhs, Node rhs) { super(null, lhs, rhs); }
 
     @Override public String label() { return "MulF"; }
 
-    @Override
-    StringBuilder _print1(StringBuilder sb, BitSet visited) {
-        in(1)._print0(sb.append("("), visited);
-        in(2)._print0(sb.append("*"), visited);
-        return sb.append(")");
-    }
+    @Override protected String format() { return "(%1*%2)"; }
 
     @Override
     public Type compute() {
diff --git a/chapter12/src/main/java/com/seaofnodes/simple/node/MulNode.java b/chapter12/src/main/java/com/seaofnodes/simple/node/MulNode.java
index 9891cd45..2c13fd0f 100644
--- a/chapter12/src/main/java/com/seaofnodes/simple/node/MulNode.java
+++ b/chapter12/src/main/java/com/seaofnodes/simple/node/MulNode.java
@@ -1,21 +1,16 @@
 package com.seaofnodes.simple.node;
 
+
 import com.seaofnodes.simple.type.Type;
 import com.seaofnodes.simple.type.TypeInteger;
 
-import java.util.BitSet;
 
 public class MulNode extends Node {
     public MulNode(Node lhs, Node rhs) { super(null, lhs, rhs); }
 
     @Override public String label() { return "Mul"; }
 
-    @Override
-    StringBuilder _print1(StringBuilder sb, BitSet visited) {
-        in(1)._print0(sb.append("("), visited);
-        in(2)._print0(sb.append("*"), visited);
-        return sb.append(")");
-    }
+    @Override protected String format() { return "(%1*%2)"; }
 
     @Override
     public Type compute() {
diff --git a/chapter12/src/main/java/com/seaofnodes/simple/node/NeverNode.java b/chapter12/src/main/java/com/seaofnodes/simple/node/NeverNode.java
index e77ed653..7e42ccf9 100644
--- a/chapter12/src/main/java/com/seaofnodes/simple/node/NeverNode.java
+++ b/chapter12/src/main/java/com/seaofnodes/simple/node/NeverNode.java
@@ -1,11 +1,12 @@
 package com.seaofnodes.simple.node;
 
+import com.seaofnodes.print.ExprPrinter;
+
 import com.seaofnodes.simple.Parser;
 import com.seaofnodes.simple.type.TypeInteger;
 import com.seaofnodes.simple.type.Type;
 import com.seaofnodes.simple.type.TypeTuple;
 
-import java.util.BitSet;
 
 // "Never true" for infinite loop exits
 public class NeverNode extends IfNode {
@@ -13,7 +14,7 @@ public class NeverNode extends IfNode {
 
     @Override public String label() { return "Never"; }
 
-    @Override StringBuilder _print1(StringBuilder sb, BitSet visited) { return sb.append("Never"); }
+    @Override protected ExprPrinter<Node> _print1(ExprPrinter<Node> p) { return p.p("Never"); }
 
     @Override public Type compute() { return TypeTuple.IF_BOTH; }
 
diff --git a/chapter12/src/main/java/com/seaofnodes/simple/node/NewNode.java b/chapter12/src/main/java/com/seaofnodes/simple/node/NewNode.java
index 1c82d5f5..74ba5184 100644
--- a/chapter12/src/main/java/com/seaofnodes/simple/node/NewNode.java
+++ b/chapter12/src/main/java/com/seaofnodes/simple/node/NewNode.java
@@ -1,9 +1,10 @@
 package com.seaofnodes.simple.node;
 
+import com.seaofnodes.print.ExprPrinter;
+
 import com.seaofnodes.simple.type.Type;
 import com.seaofnodes.simple.type.TypeMemPtr;
 
-import java.util.BitSet;
 
 public class NewNode extends Node {
 
@@ -17,10 +18,8 @@ public class NewNode extends Node {
     @Override
     public String label() { return "new"; }
 
-    @Override
-    StringBuilder _print1(StringBuilder sb, BitSet visited) {
-        sb.append("new ");
-        return sb.append(_ptr._obj.str());
+    @Override protected ExprPrinter<Node> _print1(ExprPrinter<Node> p) {
+        return p.p("new ").p(_ptr._obj.str());
     }
 
 
diff --git a/chapter12/src/main/java/com/seaofnodes/simple/node/Node.java b/chapter12/src/main/java/com/seaofnodes/simple/node/Node.java
index ff8415c5..e3503a7c 100644
--- a/chapter12/src/main/java/com/seaofnodes/simple/node/Node.java
+++ b/chapter12/src/main/java/com/seaofnodes/simple/node/Node.java
@@ -1,5 +1,7 @@
 package com.seaofnodes.simple.node;
 
+import com.seaofnodes.print.BaseNode;
+
 import com.seaofnodes.simple.Parser;
 
 import com.seaofnodes.simple.IRPrinter;
@@ -16,14 +18,7 @@ import java.util.function.Function;
  * The Node class provides common functionality used by all subtypes.
  * Subtypes of Node specialize by overriding methods.
  */
-public abstract class Node implements OutNode, Cloneable {
-
-    /**
-     * Each node has a unique dense Node ID within a compilation context
-     * The ID is useful for debugging, for using as an offset in a bitvector,
-     * as well as for computing equality of nodes (to be implemented later).
-     */
-    public int _nid;
+public abstract class Node extends BaseNode<Node> implements OutNode, Cloneable {
 
     /**
      * Inputs to the node. These are use-def references to Nodes.
@@ -45,14 +40,12 @@ public abstract class Node implements OutNode, Cloneable {
      */
     public ArrayList<Node> _outputs;
 
-
     /**
      * Current computed type for this Node.  This value changes as the graph
      * changes and more knowledge is gained about the program.
      */
     public Type _type;
 
-
     /**
      * A private Global Static mutable counter, for unique node id generation.
      * To make the compiler multithreaded, this field will have to move into a TLS.
@@ -62,7 +55,7 @@ public abstract class Node implements OutNode, Cloneable {
     public static int UID() { return UNIQUE_ID; }
 
     protected Node(Node... inputs) {
-        _nid = UNIQUE_ID++; // allocate unique dense ID
+        super(UNIQUE_ID++); // allocate unique dense ID
         _inputs = new ArrayList<>();
         Collections.addAll(_inputs,inputs);
         _outputs = new ArrayList<>();
@@ -74,42 +67,6 @@ public abstract class Node implements OutNode, Cloneable {
     // Easy reading label for debugger, e.g. "Add" or "Region" or "EQ"
     public abstract String label();
 
-    // Unique label for debugging, e.g. "Add12" or "Region30" or "EQ99"
-    public String uniqueName() {
-        return label() + _nid;
-    }
-
-    // ------------------------------------------------------------------------
-
-    // Debugger Printing.
-
-    // {@code toString} is what you get in the debugger.  It has to print 1
-    // line (because this is what a debugger typically displays by default) and
-    // has to be robust with broken graph/nodes.
-    @Override
-    public final String toString() {  return print(); }
-
-    // This is a *deep* print.  This version will fail on cycles, which we will
-    // correct later when we can parse programs with loops.  We print with a
-    // tik-tok style; the common _print0 calls the per-Node _print1, which
-    // calls back to _print0;
-    public final String print() {
-        return _print0(new StringBuilder(), new BitSet()).toString();
-    }
-
-    // This is the common print: check for repeats, check for DEAD and print
-    // "DEAD" else call the per-Node print1.
-    final StringBuilder _print0(StringBuilder sb, BitSet visited) {
-        if (visited.get(_nid) && !(this instanceof ConstantNode) )
-            return sb.append(label());
-        visited.set(_nid);
-        return isDead()
-            ? sb.append(uniqueName()).append(":DEAD")
-            : _print1(sb, visited);
-    }
-    // Every Node implements this; a partial-line recursive print
-    abstract StringBuilder _print1(StringBuilder sb, BitSet visited);
-
     public String p(int depth) { return IRPrinter.prettyPrint(this,depth); }
 
     public boolean isMultiHead() { return false; }
@@ -118,6 +75,8 @@ public abstract class Node implements OutNode, Cloneable {
     // ------------------------------------------------------------------------
     // Graph Node & Edge manipulation
 
+    @Override public String typeName() { return _type==null ? null : _type.toString(); }
+
     /**
      * Gets the ith input node
      * @param i Offset of the input node
@@ -258,7 +217,6 @@ public abstract class Node implements OutNode, Cloneable {
     // Test "keep" status
     public boolean iskeep() { return Utils.find(_outputs,null) != -1; }
 
-
     // Replace self with nnn in the graph, making 'this' go dead
     public void subsume( Node nnn ) {
         assert nnn!=this;
@@ -389,7 +347,6 @@ public abstract class Node implements OutNode, Cloneable {
         return old;
     }
 
-
     /**
      * This function rewrites the current Node into a more "idealized" form.
      * This is the bulk of our peephole rewrite rules, and we use this to
@@ -437,7 +394,6 @@ public abstract class Node implements OutNode, Cloneable {
      */
     public abstract Node idealize();
 
-
     // Some of the peephole rules get complex, and search further afield than
     // just the nearest neighbor.  These peepholes can fail the pattern match
     // on a node some distance away, and if that node ever changes we should
@@ -481,7 +437,6 @@ public abstract class Node implements OutNode, Cloneable {
         _deps.clear();
     }
 
-
     // Global Value Numbering.  Hash over opcode and inputs; hits in this table
     // are structurally equal.
     public static final HashMap<Node,Node> GVN = new HashMap<>();
@@ -503,7 +458,6 @@ public abstract class Node implements OutNode, Cloneable {
     // and can assume "this!=n" and has the same Java class.
     boolean eq( Node n ) { return true; }
 
-
     // Cached hash.  If zero, then not computed AND this Node is NOT in the GVN
     // table - and can have its edges hacked (which will change his hash
     // anyway).  If Non-Zero then this Node is IN the GVN table, or is being
@@ -519,7 +473,6 @@ public abstract class Node implements OutNode, Cloneable {
         _hash=0;                // Out of table now
     }
 
-
     // Hash of opcode and inputs
     @Override public final int hashCode() {
         if( _hash != 0 ) return _hash;
@@ -537,7 +490,6 @@ public abstract class Node implements OutNode, Cloneable {
     //
 
     /** Is this Node control-flow-graph related */
-    public boolean isCFG() { return false; }
 
     /** Is this Node Memory related */
     public boolean isMem() { return false; }
@@ -545,7 +497,6 @@ public abstract class Node implements OutNode, Cloneable {
     /** Return block start from a isCFG() */
     public Node getBlockStart() { return null; }
 
-
     // Semantic change to the graph (so NOT a peephole), used by the Parser.
     // If any input is a float, flip to a float-flavored opcode and widen any
     // non-float input.
@@ -566,7 +517,6 @@ public abstract class Node implements OutNode, Cloneable {
     }
     Node copyF() { return null; }
 
-
     // ------------------------------------------------------------------------
     // Peephole utilities
 
@@ -595,7 +545,6 @@ public abstract class Node implements OutNode, Cloneable {
         return true;
     }
 
-
     // Make a shallow copy (same class) of this Node, with given inputs and
     // empty outputs and a new Node ID.  The original inputs are ignored.
     // Does not need to be implemented in isCFG() nodes.
@@ -628,7 +577,6 @@ public abstract class Node implements OutNode, Cloneable {
         ITER_CNT = ITER_NOP_CNT = 0;
     }
 
-
     // Utility to walk the entire graph applying a function; return the first
     // not-null result.
     private static final BitSet WVISIT = new BitSet();
diff --git a/chapter12/src/main/java/com/seaofnodes/simple/node/NotNode.java b/chapter12/src/main/java/com/seaofnodes/simple/node/NotNode.java
index bb7e9265..4539f982 100644
--- a/chapter12/src/main/java/com/seaofnodes/simple/node/NotNode.java
+++ b/chapter12/src/main/java/com/seaofnodes/simple/node/NotNode.java
@@ -1,19 +1,15 @@
 package com.seaofnodes.simple.node;
 
+
 import com.seaofnodes.simple.Utils;
 import com.seaofnodes.simple.type.*;
-import java.util.BitSet;
 
 public class NotNode extends Node {
     public NotNode(Node in) { super(null, in); }
 
     @Override public String label() { return "Not"; }
 
-    @Override
-    StringBuilder _print1(StringBuilder sb, BitSet visited) {
-        in(1)._print0(sb.append("(!"), visited);
-        return sb.append(")");
-    }
+    @Override protected String format() { return "(!%1)"; }
 
     @Override
     public Type compute() {
diff --git a/chapter12/src/main/java/com/seaofnodes/simple/node/PhiNode.java b/chapter12/src/main/java/com/seaofnodes/simple/node/PhiNode.java
index 277c16d1..8dfa04cf 100644
--- a/chapter12/src/main/java/com/seaofnodes/simple/node/PhiNode.java
+++ b/chapter12/src/main/java/com/seaofnodes/simple/node/PhiNode.java
@@ -1,10 +1,11 @@
 package com.seaofnodes.simple.node;
 
+import com.seaofnodes.print.ExprPrinter;
+
 import com.seaofnodes.simple.type.Type;
 import com.seaofnodes.simple.type.TypeMem;
 import com.seaofnodes.simple.Utils;
 
-import java.util.BitSet;
 
 public class PhiNode extends Node {
 
@@ -23,18 +24,12 @@ public class PhiNode extends Node {
     @Override public String label() { return "Phi_"+_label; }
 
     @Override
-    StringBuilder _print1(StringBuilder sb, BitSet visited) {
+    protected ExprPrinter<Node> _print1(ExprPrinter<Node> p) {
         if( !(region() instanceof RegionNode r) || r.inProgress() )
-            sb.append("Z");
-        sb.append("Phi(");
-        for( Node in : _inputs ) {
-            if (in == null) sb.append("____");
-            else in._print0(sb, visited);
-            sb.append(",");
-        }
-        sb.setLength(sb.length()-1);
-        sb.append(")");
-        return sb;
+            p.p("Z");
+        p.p("Phi(");
+        for( Node in : _inputs ) p.n(in).p(",");
+        return p.unchar(',').close();
     }
 
     public CFGNode region() { return (CFGNode)in(0); }
diff --git a/chapter12/src/main/java/com/seaofnodes/simple/node/ProjNode.java b/chapter12/src/main/java/com/seaofnodes/simple/node/ProjNode.java
index 93239a61..e82c69b3 100644
--- a/chapter12/src/main/java/com/seaofnodes/simple/node/ProjNode.java
+++ b/chapter12/src/main/java/com/seaofnodes/simple/node/ProjNode.java
@@ -1,10 +1,11 @@
 package com.seaofnodes.simple.node;
 
+import com.seaofnodes.print.ExprPrinter;
+
 import com.seaofnodes.simple.type.Type;
 import com.seaofnodes.simple.type.TypeMem;
 import com.seaofnodes.simple.type.TypeTuple;
 
-import java.util.BitSet;
 
 public class ProjNode extends Node {
 
@@ -24,7 +25,7 @@ public class ProjNode extends Node {
     public String label() { return _label; }
 
     @Override
-    StringBuilder _print1(StringBuilder sb, BitSet visited) { return sb.append(_label); }
+    protected ExprPrinter<Node> _print1(ExprPrinter<Node> p) { return p.p(_label); }
 
     @Override public boolean isMultiTail() { return in(0).isMultiHead(); }
     @Override public boolean isMem() { return _type instanceof TypeMem; }
diff --git a/chapter12/src/main/java/com/seaofnodes/simple/node/RegionNode.java b/chapter12/src/main/java/com/seaofnodes/simple/node/RegionNode.java
index d7e934d7..cdfd10ad 100644
--- a/chapter12/src/main/java/com/seaofnodes/simple/node/RegionNode.java
+++ b/chapter12/src/main/java/com/seaofnodes/simple/node/RegionNode.java
@@ -1,5 +1,7 @@
 package com.seaofnodes.simple.node;
 
+import com.seaofnodes.print.ExprPrinter;
+
 import com.seaofnodes.simple.IterPeeps;
 import com.seaofnodes.simple.Parser;
 import com.seaofnodes.simple.Utils;
@@ -16,9 +18,8 @@ public class RegionNode extends CFGNode {
     @Override
     public String label() { return "Region"; }
 
-    @Override
-    StringBuilder _print1(StringBuilder sb, BitSet visited) {
-        return sb.append(label()).append(_nid);
+    @Override protected ExprPrinter<Node> _print1(ExprPrinter<Node> p) {
+        return p.p(label()).p(_nid);
     }
 
     @Override public boolean isMultiHead() { return true; }
diff --git a/chapter12/src/main/java/com/seaofnodes/simple/node/ReturnNode.java b/chapter12/src/main/java/com/seaofnodes/simple/node/ReturnNode.java
index 725c704f..161cc7d6 100644
--- a/chapter12/src/main/java/com/seaofnodes/simple/node/ReturnNode.java
+++ b/chapter12/src/main/java/com/seaofnodes/simple/node/ReturnNode.java
@@ -1,8 +1,9 @@
 package com.seaofnodes.simple.node;
 
+import com.seaofnodes.print.ExprPrinter;
+
 import com.seaofnodes.simple.type.*;
 
-import java.util.BitSet;
 
 /** Keeps all preceding memory effects and the return value alive: {ctrl, $mem, value}. */
 public class ReturnNode extends CFGNode {
@@ -20,10 +21,10 @@ public class ReturnNode extends CFGNode {
     public String label() { return "Return"; }
 
     @Override
-    StringBuilder _print1(StringBuilder sb, BitSet visited) {
-        sb.append("return ");
-        expr()._print0(sb, visited);
-        return sb.append(";");
+    protected ExprPrinter<Node> _print1(ExprPrinter<Node> p) {
+        p.p("return ");
+        p.n(expr());
+        return p.p(";");
     }
 
     @Override
diff --git a/chapter12/src/main/java/com/seaofnodes/simple/node/ScopeNode.java b/chapter12/src/main/java/com/seaofnodes/simple/node/ScopeNode.java
index b931e862..b408eb2f 100644
--- a/chapter12/src/main/java/com/seaofnodes/simple/node/ScopeNode.java
+++ b/chapter12/src/main/java/com/seaofnodes/simple/node/ScopeNode.java
@@ -1,5 +1,7 @@
 package com.seaofnodes.simple.node;
 
+import com.seaofnodes.print.ExprPrinter;
+
 import com.seaofnodes.simple.IterPeeps;
 import com.seaofnodes.simple.type.Type;
 import com.seaofnodes.simple.Utils;
@@ -42,20 +44,19 @@ public class ScopeNode extends Node {
     @Override public String label() { return "Scope"; }
 
     @Override
-    StringBuilder _print1(StringBuilder sb, BitSet visited) {
-        sb.append("Scope[ ");
+    protected ExprPrinter<Node> _print1(ExprPrinter<Node> p) {
+        p.p("Scope[ ");
         String[] names = reverseNames();
         for( int j=0; j<nIns(); j++ ) {
-            sb.append(names[j]).append(":");
+            p.p(names[j]).p(":");
             Node n = in(j);
             while( n instanceof ScopeNode loop ) {
-                sb.append("Lazy_");
+                p.p("Lazy_");
                 n = loop.in(j);
             }
-            n._print0(sb, visited).append(" ");
+            p.n(n).p(" ");
         }
-        sb.setLength(sb.length()-1);
-        return sb.append("]");
+        return p.unchar(' ').p("]");
     }
 
     /**
diff --git a/chapter12/src/main/java/com/seaofnodes/simple/node/StartNode.java b/chapter12/src/main/java/com/seaofnodes/simple/node/StartNode.java
index 2cedf0f6..a5d4923f 100644
--- a/chapter12/src/main/java/com/seaofnodes/simple/node/StartNode.java
+++ b/chapter12/src/main/java/com/seaofnodes/simple/node/StartNode.java
@@ -1,5 +1,7 @@
 package com.seaofnodes.simple.node;
 
+import com.seaofnodes.print.ExprPrinter;
+
 import com.seaofnodes.simple.type.*;
 import java.util.BitSet;
 import java.util.HashSet;
@@ -17,9 +19,8 @@ public class StartNode extends CFGNode implements MultiNode {
     @Override
     public String label() { return "Start"; }
 
-    @Override
-    StringBuilder _print1(StringBuilder sb, BitSet visited) {
-      return sb.append(label());
+    @Override protected ExprPrinter<Node> _print1(ExprPrinter<Node> p) {
+        return p.p(label());
     }
 
     @Override public boolean isMultiHead() { return true; }
diff --git a/chapter12/src/main/java/com/seaofnodes/simple/node/StopNode.java b/chapter12/src/main/java/com/seaofnodes/simple/node/StopNode.java
index 3ef2e4a6..b5d2d716 100644
--- a/chapter12/src/main/java/com/seaofnodes/simple/node/StopNode.java
+++ b/chapter12/src/main/java/com/seaofnodes/simple/node/StopNode.java
@@ -1,11 +1,12 @@
 package com.seaofnodes.simple.node;
 
+import com.seaofnodes.print.ExprPrinter;
+
 import com.seaofnodes.simple.Parser;
 
 import com.seaofnodes.simple.type.Type;
 import com.seaofnodes.simple.IterPeeps;
 
-import java.util.BitSet;
 
 public class StopNode extends CFGNode {
 
@@ -22,12 +23,12 @@ public class StopNode extends CFGNode {
     }
 
     @Override
-    StringBuilder _print1(StringBuilder sb, BitSet visited) {
-        if( ret()!=null ) return ret()._print0(sb, visited);
-        sb.append("Stop[ ");
+    protected ExprPrinter<Node> _print1(ExprPrinter<Node> p) {
+        if( ret()!=null ) return p.n(ret());
+        p.p("Stop[ ");
         for( Node ret : _inputs )
-            ret._print0(sb, visited).append(" ");
-        return sb.append("]");
+            p.n(ret).p(" ");
+        return p.p("]");
     }
 
     @Override public boolean blockHead() { return true; }
diff --git a/chapter12/src/main/java/com/seaofnodes/simple/node/StoreNode.java b/chapter12/src/main/java/com/seaofnodes/simple/node/StoreNode.java
index b816762b..f61afe78 100644
--- a/chapter12/src/main/java/com/seaofnodes/simple/node/StoreNode.java
+++ b/chapter12/src/main/java/com/seaofnodes/simple/node/StoreNode.java
@@ -1,10 +1,11 @@
 package com.seaofnodes.simple.node;
 
+import com.seaofnodes.print.ExprPrinter;
+
 import com.seaofnodes.simple.Utils;
 import com.seaofnodes.simple.IterPeeps;
 import com.seaofnodes.simple.type.*;
 
-import java.util.BitSet;
 
 /**
  * Store represents setting a value to a memory based object, in chapter 10
@@ -29,8 +30,8 @@ public class StoreNode extends MemOpNode {
     public Node val() { return in(3); }
 
     @Override
-    StringBuilder _print1(StringBuilder sb, BitSet visited) {
-        return sb.append(".").append(_name).append("=").append( val()).append(";");
+    protected ExprPrinter<Node> _print1(ExprPrinter<Node> p) {
+        return p.p(".").p(_name).p("=").p( val()).p(";");
     }
 
     @Override
diff --git a/chapter12/src/main/java/com/seaofnodes/simple/node/SubFNode.java b/chapter12/src/main/java/com/seaofnodes/simple/node/SubFNode.java
index 27bbda8d..2d218a03 100644
--- a/chapter12/src/main/java/com/seaofnodes/simple/node/SubFNode.java
+++ b/chapter12/src/main/java/com/seaofnodes/simple/node/SubFNode.java
@@ -1,21 +1,16 @@
 package com.seaofnodes.simple.node;
 
+
 import com.seaofnodes.simple.type.Type;
 import com.seaofnodes.simple.type.TypeFloat;
 
-import java.util.BitSet;
 
 public class SubFNode extends Node {
     public SubFNode(Node lhs, Node rhs) { super(null, lhs, rhs); }
 
     @Override public String label() { return "SubF"; }
 
-    @Override
-    StringBuilder _print1(StringBuilder sb, BitSet visited) {
-        in(1)._print0(sb.append("("), visited);
-        in(2)._print0(sb.append("-"), visited);
-        return sb.append(")");
-    }
+    @Override protected String format() { return "(%1-%2)"; }
 
     @Override
     public Type compute() {
diff --git a/chapter12/src/main/java/com/seaofnodes/simple/node/SubNode.java b/chapter12/src/main/java/com/seaofnodes/simple/node/SubNode.java
index 4ae302f0..f36f2af5 100644
--- a/chapter12/src/main/java/com/seaofnodes/simple/node/SubNode.java
+++ b/chapter12/src/main/java/com/seaofnodes/simple/node/SubNode.java
@@ -1,22 +1,17 @@
 package com.seaofnodes.simple.node;
 
+
 import com.seaofnodes.simple.Parser;
 import com.seaofnodes.simple.type.Type;
 import com.seaofnodes.simple.type.TypeInteger;
 
-import java.util.BitSet;
 
 public class SubNode extends Node {
     public SubNode(Node lhs, Node rhs) { super(null, lhs, rhs); }
 
     @Override public String label() { return "Sub"; }
 
-    @Override
-    StringBuilder _print1(StringBuilder sb, BitSet visited) {
-        in(1)._print0(sb.append("("), visited);
-        in(2)._print0(sb.append("-"), visited);
-        return sb.append(")");
-    }
+    @Override protected String format() { return "(%1-%2)"; }
 
     @Override
     public Type compute() {
diff --git a/chapter12/src/main/java/com/seaofnodes/simple/node/ToFloatNode.java b/chapter12/src/main/java/com/seaofnodes/simple/node/ToFloatNode.java
index fde483d6..26cf50e1 100644
--- a/chapter12/src/main/java/com/seaofnodes/simple/node/ToFloatNode.java
+++ b/chapter12/src/main/java/com/seaofnodes/simple/node/ToFloatNode.java
@@ -1,20 +1,17 @@
 package com.seaofnodes.simple.node;
 
+
 import com.seaofnodes.simple.type.Type;
 import com.seaofnodes.simple.type.TypeFloat;
 import com.seaofnodes.simple.type.TypeInteger;
 
-import java.util.BitSet;
 
 public class ToFloatNode extends Node {
     public ToFloatNode(Node lhs) { super(null, lhs); }
 
     @Override public String label() { return "ToFloat"; }
 
-    @Override
-    StringBuilder _print1(StringBuilder sb, BitSet visited) {
-        return in(1)._print0(sb.append("(flt)"), visited);
-    }
+    @Override protected String format() { return "(flt)%1"; }
 
     @Override
     public Type compute() {
diff --git a/chapter12/src/main/java/com/seaofnodes/simple/node/XCtrlNode.java b/chapter12/src/main/java/com/seaofnodes/simple/node/XCtrlNode.java
index 83779dd2..056dfba1 100644
--- a/chapter12/src/main/java/com/seaofnodes/simple/node/XCtrlNode.java
+++ b/chapter12/src/main/java/com/seaofnodes/simple/node/XCtrlNode.java
@@ -1,13 +1,14 @@
 package com.seaofnodes.simple.node;
 
+import com.seaofnodes.print.ExprPrinter;
+
 import com.seaofnodes.simple.Parser;
 import com.seaofnodes.simple.type.Type;
-import java.util.BitSet;
 
 public class XCtrlNode extends CFGNode {
     public XCtrlNode( ) { super(Parser.START); }
     @Override public String label() { return "Xctrl"; }
-    @Override StringBuilder _print1(StringBuilder sb, BitSet visited) { return sb.append("Xctrl"); }
+    @Override protected ExprPrinter<Node> _print1(ExprPrinter<Node> p) { return p.p("Xctrl"); }
     @Override  public Type compute() { return Type.XCONTROL; }
     @Override public Node idealize() { return null; }
 }
diff --git a/chapter12/src/main/java/com/seaofnodes/simple/print/SimpleGraphAdapter.java b/chapter12/src/main/java/com/seaofnodes/simple/print/SimpleGraphAdapter.java
index 8af87a2b..e65963db 100644
--- a/chapter12/src/main/java/com/seaofnodes/simple/print/SimpleGraphAdapter.java
+++ b/chapter12/src/main/java/com/seaofnodes/simple/print/SimpleGraphAdapter.java
@@ -1,43 +1,20 @@
 package com.seaofnodes.simple.print;
 
 import com.seaofnodes.graph.GraphAdapter;
-import com.seaofnodes.graph.GraphSnapshot;
 import com.seaofnodes.graph.GraphSnapshot.*;
 import com.seaofnodes.simple.node.*;
 import com.seaofnodes.simple.node.Node;
 import com.seaofnodes.simple.type.TypeMem;
-import java.util.ArrayList;
 
 /** Chapter 12's view of the IR; browser, transport and layout are shared. */
 public class SimpleGraphAdapter extends GraphAdapter<Node> {
-    @Override protected boolean dead(Node n) { return n.isDead(); }
-    @Override protected int id(Node n) { return n._nid; }
-    @Override protected int nIns(Node n) { return n.nIns(); }
-    @Override protected Node in(Node n, int idx) { return n.in(idx); }
-    @Override protected int nOuts(Node n) { return n.nOuts(); }
-    @Override protected Node out(Node n, int idx) { return n.out(idx); }
-    @Override protected int nDeps(Node n) { return n.nDeps(); }
-    @Override protected Node dep(Node n, int idx) { return n.dep(idx); }
 
-    private ArrayList<Edge> edges(Node n) {
-        var edges = new ArrayList<Edge>();
-        String[] names = n instanceof ScopeNode scope && n.nIns() != 0 ? scope.reverseNames() : null;
-        for( int i = 0; i < n.nIns(); i++ ) {
-            String name = names == null || i >= names.length ? null : names[i];
-            edges.add(new Edge(i, ref(n.in(i)), role(n, i), name));
-        }
-        return edges;
+    @Override protected String[] edgeNames(Node n) {
+        return n instanceof ScopeNode scope && n.nIns()!=0 ? scope.reverseNames() : null;
     }
+    @Override protected int projectionIndex(Node n) { return n instanceof ProjNode p ? p._idx : n instanceof CProjNode p ? p._idx : -1; }
 
-    @Override protected GraphSnapshot.Node desc(Node n) {
-        Projection proj = n instanceof ProjNode p ? new Projection(ref(n.in(0)), p._idx)
-            : n instanceof CProjNode p ? new Projection(ref(n.in(0)), p._idx) : null;
-        String label = n.label();
-        return new GraphSnapshot.Node(n._nid, label == null ? n.getClass().getSimpleName() : label,
-                                      n._type == null ? null : n._type.toString(), kind(n), edges(n), proj);
-    }
-
-    private Kind kind(Node n) {
+    @Override protected Kind kind(Node n) {
         if( n instanceof StopNode ) return Kind.STOP;
         if( n instanceof ScopeNode ) return Kind.SCOPE;
         if( n instanceof StartNode ) return Kind.CTRL;
@@ -47,7 +24,7 @@ public class SimpleGraphAdapter extends GraphAdapter<Node> {
         return n.isCFG() ? Kind.CTRL : isMem(n) ? Kind.MEM : Kind.DATA;
     }
 
-    private Role role(Node n, int i) {
+    @Override protected Role role(Node n, int i) {
         if( n instanceof ScopeNode || n instanceof ConstantNode || n instanceof XCtrlNode ) return Role.ASSOC;
         if( n instanceof PhiNode ) return i == 0 ? Role.ASSOC : isMem(n) ? Role.MEM : Role.DATA;
         if( n instanceof ProjNode || n instanceof CProjNode ) return n.isCFG() ? Role.CTRL : isMem(n) ? Role.MEM : Role.DATA;