X-Git-Url: https://git.lukelau.me/?p=scheme.git;a=blobdiff_plain;f=ast.scm;h=b70317a70e6fd3a14aa9fab5c94be57991427f2e;hp=9af36531e7ef38bb1affc652eb09c5afa46a3dcc;hb=8e106ca13666680051f91ab3f49ce2bd7e19ead7;hpb=86531822ef58c5b29751976f5b41d1c631bdd459

diff --git a/ast.scm b/ast.scm
index 9af3653..b70317a 100644
--- a/ast.scm
+++ b/ast.scm
@@ -1,3 +1,5 @@
+(load "utils.scm")
+
 (define (ast-type x)
   (define (builtin? x)
     (case x
@@ -33,7 +35,7 @@
     ('app (map f x))
     ('lambda `(lambda ,(lambda-args x) ,(f (lambda-body x))))
     ('if `(if ,@(map f (cdr x))))
-    ('stack `(stack ,(cadr x) ,(map f (caddr x))))
+    ('stack `(stack ,(cadr x) ,(f (caddr x))))
     (else x)))
 
 (define (ast-collect f x)
@@ -75,23 +77,62 @@
     ['stack (either (p x) (inner (caddr x)))]
     [else (p x)]))
 
-(define (let-bindings e)
-  (define (pattern-match binding body)
-    (if (eqv? (ast-type binding) 'var)
-	(list (cons binding body))
-	(let* ([constructor (car binding)]
-	       [destructor (lambda (i) (dtor-name constructor i))])
-	  (flat-map (lambda (y i)
-		      (pattern-match y `((,(destructor i) ,@body))))
-		    (cdr binding)
-		    (range 0 (length (cdr binding)))))))
-  (flat-map (lambda (x) (pattern-match (car x) (cdr x))) (cadr e)))
+(define let-bindings cadr)
 (define let-body cddr)
 
+					; (let ([(foo a b) (foo 123 345)]) a)
+					;   |
+					;   v
+					; (let ([a (foo~0 (foo 123 345)]
+                                        ;       [b (foo~1 (foo 123 345)]) a)
+(define (expand-pattern-matches program)
+  (define (go x)
+    (define (pattern-match binding)
+      (let ([binding-name (car binding)]
+	    [body (cadr binding)])
+	(if (eqv? (ast-type binding-name) 'var)
+	    (list (list binding-name body))
+	    
+	    (let* ([sum-name (car binding-name)]
+		   [destructor (lambda (i) (dtor-name sum-name i))]
+		   [products (cdr binding-name)]
+
+		   [data-layouts (program-data-layouts program)]
+
+		   [type (data-tor-type data-layouts sum-name)]
+
+		   [sums (cdr (assoc type data-layouts))]
+		   [sum (assoc sum-name sums)]
+		   
+		   [expected-number (length (cdr sum))])
+
+					; assert that we only do a let pattern match on an ADT with exactly one sum
+	      (when (not (= 1 (length sums)))
+		(error #f (format "Cannot pattern match a ~a in a let since it has ~a possible constructors"
+				  type
+				  (length sums))))
+
+					; assert that there is the correct number of bindings
+	      (when (not (= (length products)
+			    expected-number))
+		(error #f (format "Got ~a bindings: expected ~a for ~a"
+			       (length products)
+			       expected-number
+			       binding)))
+	      
+	      (flat-map (lambda (y i)
+			  (pattern-match (list y `(,(destructor i) ,body))))
+			products
+			(range 0 (length products)))))))
+    (case (ast-type x)
+      ['let `(let ,(flat-map pattern-match (let-bindings x))
+	       ,@(map go (let-body x)))]
+      [else (ast-traverse go x)]))
+  (program-map-exprs go program))
+
 (define (lambda? x)
   (and (list? x) (eq? (car x) 'lambda)))
 
-
 (define (statement-type x)
   (cond
    [(and (list? x)
@@ -112,12 +153,24 @@
   (filter (lambda (x) (eqv? (statement-type x) 'defines))
 	  program))
 
+(define (program-map-exprs f program)
+  (map (lambda (x)
+	 (case (statement-type x)
+	   ['expr (f x)]
+	   [else x]))
+       program))
+
 (define (program-body program)
   ; hack to have multi-expression bodies
   `(let ()
      ,@(filter (lambda (x) (eqv? (statement-type x) 'expr))
 	       program)))
 
+(define (data-tor-type data-layouts tor)
+  (let* ([tors (flat-map data-tors data-layouts)]
+	 [info (cadr (assoc tor tors))])
+    (car info)))
+
 					; a data tor is either a constructor or destructor for an ADT
 					; data-tors returns constructors and destructors for a data-layout
 					; (data A (foo Int Bool)
@@ -278,26 +331,3 @@
 	   (strong-connect v)))
        (car graph)))
     result))
-
-
-					; utils
-
-(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)))))
-
-
-(define-syntax push!
-  (syntax-rules ()
-    ((_ s x) (set! s (cons x s)))))
-
-(define-syntax pop!
-  (syntax-rules ()
-    ((_ s) (let ([x (car s)])
-	     (set! s (cdr s))
-	     x))))