From: Charles Oliver Nutter <charles.nutter@...>
Date: 2009-05-14T23:03:06+09:00
Subject: Re: [bikeshed] Syntactic sugar idea

Robert Klemme wrote:
> That's likely only implementation.  Then there is testing,
> documentation and before that checking that there are no negative
> effects of the change.  If there are - and there seems to be evidence
> that this is the case in Mark's posting - those negative effects also
> count as costs...

Bah, I say.

~/projects/jruby ➔ jruby -X-C -e '[1,2,3].each {puts $it}'
1
2
3

Diff follows.

diff --git a/src/org/jruby/RubyGlobal.java b/src/org/jruby/RubyGlobal.java
index f25bd42..c107a7b 100644
--- a/src/org/jruby/RubyGlobal.java
+++ b/src/org/jruby/RubyGlobal.java
@@ -199,6 +199,7 @@ public class RubyGlobal {

          runtime.defineVariable(new ErrorInfoGlobalVariable(runtime, 
"$!", runtime.getNil()));
          runtime.defineVariable(new NonEffectiveGlobalVariable(runtime, 
"$=", runtime.getFalse()));
+        runtime.defineVariable(new ImplicitItGlobalVariable(runtime, 
"$it"));

          if(runtime.getInstanceConfig().getInputFieldSeparator() == null) {
              runtime.defineVariable(new GlobalVariable(runtime, "$;", 
runtime.getNil()));
@@ -320,6 +321,24 @@ public class RubyGlobal {
          }
      }

+    private static class ImplicitItGlobalVariable extends GlobalVariable {
+        public ImplicitItGlobalVariable(Ruby runtime, String name) {
+            super(runtime, name, null);
+        }
+
+        @Override
+        public IRubyObject set(IRubyObject value) {
+            return 
runtime.getCurrentContext().getCurrentScope().setImplicitArg(value);
+        }
+
+        @Override
+        public IRubyObject get() {
+            IRubyObject obj = 
runtime.getCurrentContext().getCurrentScope().getImplicitArg();
+            if (obj == null) obj = runtime.getNil();
+            return obj;
+        }
+    }
+
      private static class LastExitStatusVariable extends GlobalVariable {
          public LastExitStatusVariable(Ruby runtime, String name) {
              super(runtime, name, runtime.getNil());
diff --git a/src/org/jruby/runtime/DynamicScope.java 
b/src/org/jruby/runtime/DynamicScope.java
index e2f6e90..9ad9deb 100644
--- a/src/org/jruby/runtime/DynamicScope.java
+++ b/src/org/jruby/runtime/DynamicScope.java
@@ -39,6 +39,8 @@ public abstract class DynamicScope {
      // been called.
      protected DynamicScope evalScope;

+    protected IRubyObject implicitArg;
+
      protected DynamicScope(StaticScope staticScope, DynamicScope parent) {
          this.staticScope = staticScope;
          this.parent = parent;
@@ -165,6 +167,14 @@ public abstract class DynamicScope {
          return staticScope.getAllNamesInScope();
      }

+    public IRubyObject getImplicitArg() {
+        return implicitArg;
+    }
+
+    public IRubyObject setImplicitArg(IRubyObject implicitArg) {
+        return this.implicitArg = implicitArg;
+    }
+
      /**
       * Get backref
       */
diff --git a/src/org/jruby/runtime/InterpretedBlock.java 
b/src/org/jruby/runtime/InterpretedBlock.java
index 8015be8..4291066 100644
--- a/src/org/jruby/runtime/InterpretedBlock.java
+++ b/src/org/jruby/runtime/InterpretedBlock.java
@@ -162,6 +162,7 @@ public class InterpretedBlock extends BlockBody {
          Frame lastFrame = pre(context, null, binding);

          try {
+            context.getCurrentScope().setImplicitArg(value);
              if (hasVarNode) {
                  setupBlockArg(context, varNode, value, self);
              }