Formulate destructors properly

[scheme.git] / ast.scm

diff --git a/ast.scm b/ast.scm
index 3b4d164b9e23fa71a1c3547c01dd6a20fbe13dac..5064ca554bc8033bdbc0b483ac79249cd3312f73 100644 (file)
--- a/ast.scm
+++ b/ast.scm
@@ -75,7 +75,7 @@
     (if (eqv? (ast-type x) 'var)
        (list (cons x body))
        (let* ([constructor (car x)]
-             [destructor (lambda (i) `(destruct ,i ,constructor))])
+              [destructor (lambda (i) (dtor-name constructor i))])
          (flat-map (lambda (y i)
                      (pattern-match y (list (destructor i) body)))
                    (cdr x)
@@ -108,6 +108,48 @@
      ,@(filter (lambda (x) (eqv? (statement-type x) 'expr))
               program)))
 
+                                       ; gets both constructors and destructors
+                                       ; (data A (foo Int Bool)
+                                       ;         (bar Bool))
+                                       ;        |
+                                       ;        v
+                                       ; (foo . (abs Int (abs Bool A)))
+                                       ; (foo~0 . (abs A Int)
+                                       ; (foo~1 . (abs A Bool)
+                                       ; (bar . (abs Bool A)
+                                       ; (bar~0 . (abs A Bool)
+
+(define (data-tors data-def)
+  (define (constructor-type t products)
+    (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 `(abs ,prod-type ,part-type))))
+  
+  (let ([type-name (cadr data-def)]
+        [ctors (cddr data-def)])
+    (fold-right
+     (lambda (ctor acc)       
+       (let* ([ctor-name (car ctor)]
+             [products (cdr ctor)]
+             
+             [maker (cons ctor-name (constructor-type type-name products))]
+             
+             [dtors (map (lambda (t i) (destructor ctor-name type-name t i))
+                         products
+                         (range 0 (length products)))])
+        
+        (cons maker (append dtors acc))))
+     '()
+     ctrs)))
+
+(define (dtor-name ctor-name index)
+  (string->symbol
+   (string-append (symbol->string ctor-name)
+                 "~"
+                 (number->string index))))
+
 ; for use in normalized form
 (define lambda-arg caadr)
 ; for use elsewhere