From 4337829fd4b0e2766e95233f1ba4f11af5163452 Mon Sep 17 00:00:00 2001
From: Eduardo Julian
Date: Sat, 30 Jul 2016 14:23:05 -0400
Subject: - Now streamlining simple "let" expressions when doing
 pattern-matching.

---
 src/lux/base.clj         |  4 ++--
 src/lux/compiler.clj     |  3 +++
 src/lux/compiler/lux.clj |  7 +++++++
 src/lux/optimizer.clj    | 23 ++++++++++++++++++-----
 4 files changed, 30 insertions(+), 7 deletions(-)

diff --git a/src/lux/base.clj b/src/lux/base.clj
index 2dc684144..be66632c5 100644
--- a/src/lux/base.clj
+++ b/src/lux/base.clj
@@ -1061,7 +1061,7 @@
     (return init)
 
     [_ _]
-    (fail "Lists don't match in size.")))
+    (assert false "Lists don't match in size.")))
 
 (defn map2% [f xs ys]
   (|case [xs ys]
@@ -1074,7 +1074,7 @@
     (return $Nil)
 
     [_ _]
-    (fail "Lists don't match in size.")))
+    (assert false "Lists don't match in size.")))
 
 (defn map2 [f xs ys]
   (|case [xs ys]
diff --git a/src/lux/compiler.clj b/src/lux/compiler.clj
index ef7fe9b1a..4548e71ab 100644
--- a/src/lux/compiler.clj
+++ b/src/lux/compiler.clj
@@ -88,6 +88,9 @@
         (&o/$case ?value [?pm ?bodies])
         (&&case/compile-case (partial compile-expression $begin) ?value ?pm ?bodies)
 
+        (&o/$let _value _register _body)
+        (&&lux/compile-let (partial compile-expression $begin) _value _register _body)
+
         (&o/$function ?arity ?scope ?env ?body)
         (&&lambda/compile-function compile-expression &/$None ?arity ?scope ?env ?body)
 
diff --git a/src/lux/compiler/lux.clj b/src/lux/compiler/lux.clj
index a9cd3756f..af20a3365 100644
--- a/src/lux/compiler/lux.clj
+++ b/src/lux/compiler/lux.clj
@@ -180,6 +180,13 @@
         :let [_ (.visitJumpInsn *writer* Opcodes/GOTO $begin)]]
     (return nil)))
 
+(defn compile-let [compile _value _register _body]
+  (|do [^MethodVisitor *writer* &/get-writer
+        _ (compile _value)
+        :let [_ (.visitVarInsn *writer* Opcodes/ASTORE _register)]
+        _ (compile _body)]
+    (return nil)))
+
 (defn ^:private compile-def-type [compile ?body]
   (|do [:let [?def-type (|case ?body
                           [[?def-type ?def-cursor] (&a/$ann ?def-value ?type-expr ?def-value-type)]
diff --git a/src/lux/optimizer.clj b/src/lux/optimizer.clj
index 3e739d511..4788536fe 100644
--- a/src/lux/optimizer.clj
+++ b/src/lux/optimizer.clj
@@ -26,6 +26,7 @@
 
   ;; Purely for optimizations
   ("loop" 1)
+  ("let" 3)
   )
 
 ;; For pattern-matching
@@ -321,6 +322,13 @@
 
       ($loop args)
       (&/T [meta ($loop (&/|map (partial shift-function-body old-scope new-scope own-body?) args))])
+
+      ($let _value _register _body)
+      (&/T [meta ($let (shift-function-body old-scope new-scope own-body? _value)
+                       (if own-body?
+                         (inc _register)
+                         _register)
+                       (shift-function-body old-scope new-scope own-body? _body))])
       
       _
       body
@@ -395,11 +403,16 @@
         (&/T [meta ($apply (pass-0 func) (&/|map pass-0 args))])
         
         (&a/$case value branches)
-        (&/T [meta ($case (pass-0 value)
-                          (optimize-pm (&/|map (fn [branch]
-                                                 (|let [[_pattern _body] branch]
-                                                   (&/T [_pattern (pass-0 _body)])))
-                                               branches)))])
+        (|case branches
+          (&/$Cons [(&a-case/$StoreTestAC _register) _body] (&/$Nil))
+          (&/T [meta ($let (pass-0 value) _register (pass-0 _body))])
+
+          _
+          (&/T [meta ($case (pass-0 value)
+                            (optimize-pm (&/|map (fn [branch]
+                                                   (|let [[_pattern _body] branch]
+                                                     (&/T [_pattern (pass-0 _body)])))
+                                                 branches)))]))
         
         (&a/$lambda scope captured body)
         (|case (pass-0 body)
-- 
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