X-Git-Url: https://git.lukelau.me/?p=scheme.git;a=blobdiff_plain;f=ast.scm;h=1a4afe21f3258d829c4f305ea78fd2f804cca2ad;hp=469a96f7162cb09c77dac0ed71b971dcbbd179a0;hb=25ef5a684dec5eedfc4e34a12b00a04e2d6b2b1b;hpb=a64f7097fa246c19a4c69d0aad65e60378273887

diff --git a/ast.scm b/ast.scm
index 469a96f..1a4afe2 100644
--- a/ast.scm
+++ b/ast.scm
@@ -71,8 +71,16 @@
     [else (p x)]))
 
 (define (let-bindings e)
-  (define (extract x)  ) ; TODO
-  (flat-map extract (cadr e))
+  (define (pattern-match x body)
+    (if (eqv? (ast-type x) 'var)
+	(cons x body)
+	(let* ([constructor (car x)]
+	      [destructor (lambda (i) `(destruct ,i ,constructor))])
+	  (flat-map (lambda (y i)
+		      (pattern-match y (list (destructor i) body)))
+		    (cdr x)
+		    (range 0 (length (cdr x)))))))
+  (flat-map (lambda (x) (pattern-match (car x) (cdr x))) (cadr e)))
 (define let-body cddr)
 
 (define (lambda? x)
@@ -107,7 +115,12 @@
 (define lambda-body caddr)
 
 					; utils
-(define (flat-map f x) (fold-left append '() (map f x)))
+(define (range s n)
+  (if (= 0 n) '()
+      (append (range s (- n 1))
+	      (list (+ s (- n 1))))))
+
+(define (flat-map f . xs) (fold-left append '() (apply map (cons f xs))))
 (define (repeat x n) (if (<= n 0) '()
 			 (cons x (repeat x (- n 1)))))