X-Git-Url: https://git.lukelau.me/?p=scheme.git;a=blobdiff_plain;f=ast.scm;h=109ce91a49ff95f7857550c0119f958b90caeefd;hp=b3f21bd07d6d07ba2b64017cff0a365cbf77abd4;hb=d6b60d54bc90e5ebdc643d05d0b806ae7fd8aa7c;hpb=006b94f5a24a794665788737fec8d54086284317

diff --git a/ast.scm b/ast.scm
index b3f21bd..109ce91 100644
--- a/ast.scm
+++ b/ast.scm
@@ -1,3 +1,5 @@
+(load "utils.scm")
+
 (define (ast-type x)
   (define (builtin? x)
     (case x
@@ -15,6 +17,7 @@
       ('if 'if)
       ('let 'let)
       ('lambda 'lambda)
+      ('case 'case)
       ('closure 'closure) ; only available in codegen
       ('static-string 'static-string) ; only available in codegen
       ('stack 'stack) ; only available in codegen (tag that value is passed via stack)
@@ -33,7 +36,11 @@
     ('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))))
+    ('case `(case ,(f (case-switch x))
+	      ,@(map (lambda (x)
+		       (list (car x) (f (cadr x))))
+		     (case-cases x))))
+    ('stack `(stack ,(cadr x) ,(f (caddr x))))
     (else x)))
 
 (define (ast-collect f x)
@@ -48,6 +55,9 @@
 		     (inner (lambda-body x)))]
     ['if (append (f x)
 		 (flat-map inner (cdr x)))]
+    ['case (append (f x)
+		   (inner (case-switch x))
+		   (flat-map inner (map cadr (case-cases x))))]
     ['stack (append (f x)
 		    (inner (caddr x)))]
     [else (f x)]))
@@ -78,6 +88,45 @@
 (define let-bindings cadr)
 (define let-body cddr)
 
+(define case-switch cadr)
+(define case-cases cddr)
+
+;; (define (verify-cases data-layouts annotated-program)
+
+;;   (define allowed-match-ast-types    
+;;     '((Int . (int-literal var))
+;;       (Bool . (bool-literal var))
+;;       (String . (string-literal var))))
+
+;;   (define (check-pattern switch-type pat)
+
+;;     (define (impossible-match)
+;;       (error "Can't pattern match ~a with ~a" switch-type (ann-expr pat)))
+
+;;     (if (assoc switch-type data-layouts)
+;; 	(begin
+;; 	  (let ([sums (cdr (assoc switch-type data-layouts))])
+;; 	    (unless (eqv? (ast-type (ann-expr pat)) 'var) (impossible-match))
+;; 	    (unless (assoc (car (ann-expr pat)) sums) (impossible-match))
+;; 	    (unless 
+;; 	  )
+;;        (begin
+;; 	 (unless (assoc switch-type allowed-match-ast-types)
+;; 	   (error #f "Can't pattern match on ~a" switch-type))
+	 
+;; 	 (let ([allowed (cdr (assoc switch-type allowed-match-ast-types))])
+;; 	   (unless (assoc (ast-type (ann-expr pat)) allowed) (impossible-match)))))))
+
+  
+;;   (let ([expr (ann-expr annotated-program)])
+;;     (case (ast-type expr)
+;;       ['case
+;; 	  (let* ([switch-type (ann-type (case-switch expr))]
+;; 		 [allowed (cdr (assoc switch-type allowed-match-ast-types))])
+;; 	    (for-each 
+;; 	      []))]))))
+
+
 					; (let ([(foo a b) (foo 123 345)]) a)
 					;   |
 					;   v
@@ -85,7 +134,7 @@
                                         ;       [b (foo~1 (foo 123 345)]) a)
 (define (expand-pattern-matches program)
   (define (go x)
-    (define (pattern-match binding)
+    (define (let-pattern-match binding)
       (let ([binding-name (car binding)]
 	    [body (cadr binding)])
 	(if (eqv? (ast-type binding-name) 'var)
@@ -99,10 +148,17 @@
 
 		   [type (data-tor-type data-layouts sum-name)]
 
-		   [sum (assoc sum-name (cdr (assoc type data-layouts)))]
+		   [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))
@@ -112,11 +168,12 @@
 			       binding)))
 	      
 	      (flat-map (lambda (y i)
-			  (pattern-match (list y `(,(destructor i) ,body))))
+			  (let-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))
+      ['let `(let ,(flat-map let-pattern-match (let-bindings x))
 	       ,@(map go (let-body x)))]
       [else (ast-traverse go x)]))
   (program-map-exprs go program))
@@ -169,10 +226,10 @@
 					;        |
 					;        v
 					; (foo   . ((A foo constructor) . (abs Int (abs Bool A))))
-					; (foo~0 . ((A foo 0)           . (abs A Int)))
-					; (foo~1 . ((A foo 1)           . (abs A Bool)))
+					; (foo~0 . ((A foo 0 Int)       . (abs A Int)))
+					; (foo~1 . ((A foo 1 Bool)      . (abs A Bool)))
 					; (bar   . ((A bar constructor) . (abs Bool A)))
-					; (bar~0 . ((A bar 0)           . (abs A Bool)))
+					; (bar~0 . ((A bar 0 Bool)      . (abs A Bool)))
 					;  ------+-------------------------------------
 					;  tor   | info                 | type
 
@@ -181,8 +238,9 @@
     (fold-right (lambda (x acc) `(abs ,x ,acc)) t products))
 
   (define (destructor ctor-name prod-type part-type index)
-    (let ([name (dtor-name ctor-name index)])
-      (cons name (cons (list prod-type ctor-name index) `(abs ,prod-type ,part-type)))))
+    (let* ([name (dtor-name ctor-name index)]
+	   [info (list prod-type ctor-name index part-type)])
+      (cons name (cons info `(abs ,prod-type ,part-type)))))
   
   (let ([type-name (car data-layout)]
         [ctors (cdr data-layout)])
@@ -322,26 +380,3 @@
 	   (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))))