Fix typo: spline -> spine in AddNode (chapters 4-8) (#248)

The add canonicalization builds a left-leaning chain of AddNodes -- the
"spine" -- with off-spine operands hanging off each in(2). The comparator
and its comments were spelled "spline" (a curve / mechanical part), which
was already inconsistent with the goal comment in the same method:

    // Goal: a left-spine set of adds, with constants on the rhs

Chapters 9 and later already use "spine" / "spine_cmp"; this brings the
earlier chapters in line.

Comment and private-method-name only, no behavior change.

Co-authored-by: Claude Opus 5 <noreply@anthropic.com>

1 files changed, 5 insertions, 5 deletions

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 5720aca4..7e08a207 100644
--- a/chapter04/src/main/java/com/seaofnodes/simple/node/AddNode.java
+++ b/chapter04/src/main/java/com/seaofnodes/simple/node/AddNode.java
@@ -63,7 +63,7 @@ public class AddNode extends Node {
 
         // Now we might see (add add non) or (add non non) but never (add non add) nor (add add add)
         if( !(lhs instanceof AddNode) )
-            return spline_cmp(lhs,rhs) ? swap12() : null;
+            return spine_cmp(lhs,rhs) ? swap12() : null;
 
         // Now we only see (add add non)
 
@@ -72,22 +72,22 @@ public class AddNode extends Node {
         if( lhs.in(2)._type.isConstant() && t2.isConstant() )
             return new AddNode(lhs.in(1),new AddNode(lhs.in(2),rhs).peephole());
 
-        // Now we sort along the spline via rotates, to gather similar things together.
+        // Now we sort along the spine via rotates, to gather similar things together.
 
         // Do we rotate (x + y) + z
         // into         (x + z) + y ?
-        if( spline_cmp(lhs.in(2),rhs) )
+        if( spine_cmp(lhs.in(2),rhs) )
             return new AddNode(new AddNode(lhs.in(1),rhs).peephole(),lhs.in(2));
 
         return null;
     }
 
-    // Compare two off-spline nodes and decide what order they should be in.
+    // Compare two off-spine nodes and decide what order they should be in.
     // Do we rotate ((x + hi) + lo) into ((x + lo) + hi) ?
     // Generally constants always go right, then others.
     // Ties with in a category sort by node ID.
     // TRUE if swapping hi and lo.
-    static boolean spline_cmp( Node hi, Node lo ) {
+    static boolean spine_cmp( Node hi, Node lo ) {
         if( lo._type.isConstant() ) return false;
         if( hi._type.isConstant() ) return true ;