From 8f5cd3917fd3a94ae99710a614dce9028f9afad8 Mon Sep 17 00:00:00 2001
From: Eduardo Julian
Date: Fri, 12 Dec 2014 19:07:58 -0400
Subject: Added let (local vars).

---
 src/lang.clj          |  1 -
 src/lang/analyser.clj | 13 +++++++++++++
 src/lang/compiler.clj | 14 ++++++++++++++
 src/lang/parser.clj   | 13 ++++---------
 4 files changed, 31 insertions(+), 10 deletions(-)

(limited to 'src')

diff --git a/src/lang.clj b/src/lang.clj
index a5aef4f6e..83862bb2f 100644
--- a/src/lang.clj
+++ b/src/lang.clj
@@ -52,7 +52,6 @@
 
   ;; TODO: Define functions as classes inheriting Function.
   ;; TODO: Add tuples.
-  ;; TODO: Add let.
   ;; TODO: Add pattern-matching.
   ;; TODO: Do tail-call optimization.
   ;; TODO: Add macros.
diff --git a/src/lang/analyser.clj b/src/lang/analyser.clj
index 98543e13e..811cc93ea 100644
--- a/src/lang/analyser.clj
+++ b/src/lang/analyser.clj
@@ -24,6 +24,10 @@
                      (assoc-in [:defs (:name state) name] desc)
                      (assoc-in [:env :mappings name] (annotated [::global (:name state) name] (:type desc)))) nil]]))
 
+(def ^:private next-local-idx
+  (fn [state]
+    [::&util/ok [state (-> state :env :counter)]]))
+
 (defn ^:private with-local [name type body]
   (fn [state]
     (let [=return (body (update-in state [:env] #(-> %
@@ -108,6 +112,14 @@
          =else (analyse-form* ?else)]
     (return (annotated [::if =test =then =else] ::&type/nothing))))
 
+(defanalyser analyse-let
+  [::&parser/let ?label ?value ?body]
+  (exec [=value (analyse-form* ?value)
+         idx next-local-idx
+         =body (with-local ?label =value
+                 (analyse-form* ?body))]
+    (return (annotated [::let idx ?label =value =body] (:type =body)))))
+
 (defanalyser analyse-defclass
   [::&parser/defclass ?name ?fields]
   (let [=members {:fields (into {} (for [[class field] ?fields]
@@ -176,6 +188,7 @@
               analyse-dynamic-access
               analyse-fn-call
               analyse-if
+              analyse-let
               analyse-defclass
               analyse-definterface
               analyse-def
diff --git a/src/lang/compiler.clj b/src/lang/compiler.clj
index a71a66b8b..8b73720c4 100644
--- a/src/lang/compiler.clj
+++ b/src/lang/compiler.clj
@@ -127,6 +127,19 @@
     (assert (compile-form (assoc *state* :form ?else)) "CAN't COMPILE ELSE")
     (.visitLabel *writer* end-label)))
 
+(defcompiler ^:private compile-let
+  [::&analyser/let ?idx ?label ?value ?body]
+  (let [start-label (new Label)
+        end-label (new Label)
+        ?idx (int ?idx)]
+    (.visitLocalVariable *writer* ?label (->java-sig (:type ?value)) nil start-label end-label ?idx)
+    (assert (compile-form (assoc *state* :form ?value)) "CAN't COMPILE LET-VALUE")
+    (doto *writer*
+      (.visitVarInsn Opcodes/ASTORE ?idx)
+      (.visitLabel start-label))
+    (assert (compile-form (assoc *state* :form ?body)) "CAN't COMPILE LET-BODY")
+    (.visitLabel *writer* end-label)))
+
 (defcompiler ^:private compile-def
   [::&analyser/def ?form ?body]
   (match ?form
@@ -221,6 +234,7 @@
                    compile-dynamic-access
                    compile-ann-class
                    compile-if
+                   compile-let
                    compile-def
                    compile-module
                    compile-defclass
diff --git a/src/lang/parser.clj b/src/lang/parser.clj
index 2d104be94..fd50a04fb 100644
--- a/src/lang/parser.clj
+++ b/src/lang/parser.clj
@@ -93,15 +93,10 @@
     (return [::case =variant =branches])))
 
 (defparser ^:private parse-let
-  [::&lexer/list ([[::&lexer/ident "let"] [::&lexer/tuple ?bindings] ?expr] :seq)]
-  (exec [=expr (apply-m parse-form (list ?expr))
-         =bindings (do (assert (even? (count ?bindings)))
-                     (map-m (fn [[destruct expr]]
-                              (exec [=destruct (apply-m parse-form (list destruct))
-                                     =expr (apply-m parse-form (list expr))]
-                                (return [::let-binding =destruct =expr])))
-                            (partition 2 ?bindings)))]
-    (return [::let =bindings =expr])))
+  [::&lexer/list ([[::&lexer/ident "let"] [::&lexer/ident ?label] ?value ?body] :seq)]
+  (exec [=value (apply-m parse-form (list ?value))
+         =body (apply-m parse-form (list ?body))]
+    (return [::let ?label =value =body])))
 
 (defparser ^:private parse-module
   [::&lexer/list ([[::&lexer/ident "module"]] :seq)]
-- 
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