Resolve types in lambda arguments, recursively substitute

[scheme.git] / typecheck.scm

diff --git a/typecheck.scm b/typecheck.scm
index a7384294ac0e5ad2e4d7225a53cca150b93ba2ea..eaff75efbe6fdf313e0522216c5e07d2486c75ac 100644 (file)
--- a/typecheck.scm
+++ b/typecheck.scm
@@ -26,11 +26,16 @@
                                        
 (define (normalize prog) ; (+ a b) -> ((+ a) b)
   (cond
-   ((lambda? prog) (list 'lambda (lambda-arg prog) (normalize (lambda-body prog))))
+   ; (lambda (x y) (+ x y)) -> (lambda (x) (lambda (y) (+ x y)))
+   ((lambda? prog)
+    (if (> (length (lambda-args prog)) 1)
+       (list 'lambda (list (car (lambda-args prog)))
+             (normalize (list 'lambda (cdr (lambda-args prog)) (caddr prog))))
+       (list 'lambda (lambda-args prog) (normalize (caddr prog)))))
    ((app? prog)
     (if (null? (cddr prog))
        (cons (normalize (car prog)) (normalize (cdr prog))) ; (f a)
-       (normalize (cons (cons (car prog) (list (cadr prog))) (cddr prog))))) ; (f a b)
+       (list (list (normalize (car prog)) (normalize (cadr prog))) (normalize (caddr prog))))) ; (f a b)
    ((let? prog)
     (append (list 'let
                  (map (lambda (x) (cons (car x) (normalize (cdr x))))
@@ -39,11 +44,14 @@
    (else prog)))
 
 
+; we typecheck the lambda calculus only (only single arg lambdas)
 (define (typecheck prog)
   (define (check env x)
     ;; (display "check: ")
     ;; (display x)
-    ;; (display "\n")
+    ;; (display "\n\t")
+    ;; (display env)
+    ;; (newline)
     (let
        ((res
          (cond
@@ -65,17 +73,22 @@
                  
 
           ((lambda? x)
-           (let* ((new-env (cons (cons (lambda-arg x) (fresh-tvar)) env))
+           (let* ((new-env (env-insert env (lambda-arg x) (fresh-tvar)))
                   (body-type-res (check new-env (lambda-body x)))
-                  (subd-env (substitute-env (car body-type-res) new-env)))
-             ;; (display "lambda: ")
-             ;; (display body-type-res)
-             ;; (display "\n")
-             ;; (display subd-env)
-             ;; (display "\n")
+                  (cs (car body-type-res))
+                  (subd-env (substitute-env (car body-type-res) new-env))
+                  (arg-type (env-lookup subd-env (lambda-arg x)))
+                  (resolved-arg-type (substitute cs arg-type)))
+             ;; (display "lambda:\n\t")
+             ;; (display prog)
+             ;; (display "\n\t")
+             ;; (display cs)
+             ;; (display "\n\t")
+             ;; (display resolved-arg-type)
+             ;; (newline)
              (list (car body-type-res)
                    (list 'abs
-                         (env-lookup subd-env (lambda-arg x))
+                         resolved-arg-type
                          (cadr body-type-res)))))
           
           ((app? x) ; (f a)
@@ -89,7 +102,9 @@
                                  (list 'abs
                                        arg-type
                                        (fresh-tvar))))
-                  (cs (append func-c (car arg-type-res) (car func-type-res)))
+                  (cs (consolidate
+                       (consolidate func-c (car arg-type-res))
+                       (car func-type-res)))
                   
                   (resolved-func-type (substitute cs func-type))
                   (resolved-return-type (caddr resolved-func-type)))
@@ -138,24 +153,32 @@
                      (unify (caddr a) (caddr b))))
        (else (error #f "could not unify"))))
 
-
                                        ; TODO: what's the most appropriate substitution?
                                        ; should all constraints just be limited to a pair?
 (define (substitute cs t)
                                        ; gets the first concrete type
                                        ; otherwise returns the last type variable
+
   (define (get-concrete c)
-    (if (null? (cdr c))
-       (car c)
+    (let ((last (null? (cdr c))))
       (if (not (tvar? (car c)))
+         (if (abs? (car c))
+             (substitute cs (car c))
+             (car c))
+         (if last
              (car c)
-           (get-concrete (cdr c)))))
+             (get-concrete (cdr c))))))
+  (cond
+   ((abs? t) (list 'abs
+                  (substitute cs (cadr t))
+                  (substitute cs (caddr t))))
+   (else
     (fold-left
      (lambda (t c)
        (if (member t c)
           (get-concrete c)
           t))
-   t cs))
+     t cs))))
 
 (define (substitute-env cs env)
   (map (lambda (x) (cons (car x) (substitute cs (cdr x)))) env))