From: Luke Lau <luke_lau@icloud.com>
Date: Mon, 22 Jul 2019 19:41:24 +0000 (+0100)
Subject: Add recursive let-bindings
X-Git-Url: http://git.lukelau.me/?p=scheme.git;a=commitdiff_plain;h=8aacba5976424791fb51d5d36118269d32c4096a

Add recursive let-bindings
---

diff --git a/codegen.scm b/codegen.scm
index d30adc5..e1b51a6 100644
--- a/codegen.scm
+++ b/codegen.scm
@@ -51,12 +51,17 @@
 	 (inner-si (- si (* (length bindings) wordsize)))
 	 (names (map car bindings))
 	 (exprs (map cadr bindings))
-	 (inner-env (append (map cons names stack-offsets) env)))
-  (for-each (lambda (expr offset)
+
+	 ; recursive let bindings: build environment as we go
+	 (inner-env (fold-left
+		     (lambda (env name expr offset)
 		       (codegen-expr expr inner-si env)
-	      (emit "movq %rax, ~a(%rsp)" offset))
-	    exprs stack-offsets)
-  (for-each (lambda (form) (codegen-expr form inner-si inner-env)) body)))
+		       (emit "movq %rax, ~a(%rsp)" offset)
+		       (cons (cons name offset) env))
+		     env names exprs stack-offsets)))
+    (for-each (lambda (form)
+		(codegen-expr form inner-si inner-env))
+	      body)))
 
 (define (codegen-var name si env)
   (when (not (assoc name env))