From a5f2a15ec038af66c5cbce819a24c0917afe0740 Mon Sep 17 00:00:00 2001
From: "Brian T. Rice" <briantrice@gmail.com>
Date: Sat, 1 Jan 2011 20:11:22 -0800
Subject: [PATCH] Added a Binding Syntax node and implemented bindTo: to use
 it, enforcing immutable local bindings. Bindings inside blocks will
 automatically create local variables in the outermost block scope without a
 variable or binding of that name.

---
 src/lib/macro.slate   | 13 +++++++++++--
 src/syntax/node.slate | 24 ++++++++++++++++++++++++
 2 files changed, 35 insertions(+), 2 deletions(-)

diff --git a/src/lib/macro.slate b/src/lib/macro.slate
index baa2553..4cfbf96 100644
--- a/src/lib/macro.slate
+++ b/src/lib/macro.slate
@@ -172,8 +172,17 @@ node@(nodes LoadVariable traits) bindTo: value &environment: env
 
 msg@(nodes UnaryMessage traits) bindTo: value &environment: env
 [
-  nodes KeywordMessage sending: #bind:to: to:
-    {msg arguments first. nodes Literal for: msg selector. value}
+  env
+    ifNil:
+      [nodes KeywordMessage sending: #bind:to: to:
+         {msg arguments first. nodes Literal for: msg selector. value}]
+    ifNotNil:
+      [(env outermostScopeNotBinding: msg selector)
+         ifNil: [error: 'Cannot rebind']
+         ifNotNilDo:
+           [| :scope |
+            StoreVariable of: value into:
+              (scope addVariable: (nodes Binding named: msg selector))]]
 ].
 
 message@(nodes KeywordMessage traits) bindTo: val
diff --git a/src/syntax/node.slate b/src/syntax/node.slate
index 8a85e44..f8ee6d5 100644
--- a/src/syntax/node.slate
+++ b/src/syntax/node.slate
@@ -698,6 +698,21 @@ a Namespace."
   scope
 ].
 
+block@(nodes Block traits) hasVariableNamed: name
+[
+  block localVariables anySatisfy: [| :var | name =~ var name]
+].
+
+block@(nodes Block traits) outermostScopeNotBinding: name
+"Answers the outermost scope that does not have a given binding or slot."
+[| scope |
+  (block hasVariableNamed: name) ifFalse:
+    [scope := block.
+     [(scope hasVariableNamed: name) \/ [scope parentScope isSameAs: nodes Namespace]]
+       whileFalse: [scope := scope parentScope]].
+  scope
+].
+
 block@(nodes Block traits) findVariable: name
 "Searches through the current scope, and then upward, for the entry
 corresponding to the given name, and answers what it can find, or Nil if none."
@@ -963,6 +978,12 @@ var@(nodes Variable traits) deepCopy: scope
   scope findVariable: var name
 ].
 
+var@(nodes Variable traits) isImmutable [False].
+
+nodes define: #Binding &parents: {nodes Variable}.
+
+var@(nodes Binding traits) isImmutable [True].
+
 nodes define: #RestVariable &parents: {nodes Variable}.
 
 nodes define: #VariableOperation &parents: {nodes Node} &slots: {#variable}.
@@ -1003,6 +1024,9 @@ store@(nodes StoreVariable traits) of: value into: variable
 var@(nodes Variable traits) store: value
 [nodes StoreVariable of: value into: var].
 
+var@(nodes Binding traits) store: value
+[error: 'Cannot rebind'].
+
 load@(nodes LoadVariable traits) store: value
 [load variable store: value].
 
-- 
2.11.4.GIT