Resolve types in lambda arguments, recursively substitute

Also add test

diff --git a/tests.scm b/tests.scm
new file mode 100644 (file)
index 0000000..39ca240
--- /dev/null
+++ b/tests.scm
@@ -0,0 +1,10 @@
+(load "typecheck.scm")
+
+(define (test actual expected)
+  (when (not (equal? actual expected))
+    (error #f
+          (format "test failed:\nexpected: ~a\nactual:   ~a"
+                  expected actual))))
+
+(test (typecheck '(lambda (x) (+ ((lambda (y) (x y 3)) 5) 2)))
+      '(abs (abs int (abs int int)) int))

diff --git a/typecheck.scm b/typecheck.scm
index 98d1cf449fdaeed5f1b0f1eb22abf60a405d3a66..eaff75efbe6fdf313e0522216c5e07d2486c75ac 100644 (file)
--- a/typecheck.scm
+++ b/typecheck.scm
@@ -47,11 +47,11 @@
 ; we typecheck the lambda calculus only (only single arg lambdas)
 (define (typecheck prog)
   (define (check env x)
-    (display "check: ")
-    (display x)
-    (display "\n\t")
-    (display env)
-    (newline)
+    ;; (display "check: ")
+    ;; (display x)
+    ;; (display "\n\t")
+    ;; (display env)
+    ;; (newline)
     (let
        ((res
          (cond
@@ -75,15 +75,20 @@
           ((lambda? x)
            (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)
@@ -97,7 +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)))
@@ -114,13 +121,13 @@
                  (let ((return-type (substitute cs (caddr resolved-func-type))))
                    (list cs return-type))
                  (error #f "not a function")))))))
-      (display "result of ")
-      (display x)
-      (display ":\n\t")
-      (display (cadr res))
-      (display "[")
-      (display (car res))
-      (display "]\n")
+      ;; (display "result of ")
+      ;; (display x)
+      ;; (display ":\n\t")
+      ;; (display (cadr res))
+      ;; (display "[")
+      ;; (display (car res))
+      ;; (display "]\n")
       res))
   (cadr (check '() (normalize prog))))
 
@@ -146,24 +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))