Add recursive let-bindings

diff --git a/codegen.scm b/codegen.scm
index d30adc54e61a144097c3b0bb541a5835af8c028a..e1b51a60a5ac6c9fcde9f23dd4ca58e9c02f2274 100644 (file)
--- 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))