init commit

denotational-lambda.scm

@@ -0,0 +1,38 @@
+(use-modules (ice-9 match)
+             (srfi srfi-64))
+
+(define (meaning expr)
+  (match expr
+    [`(lambda (,var) ,expr)
+     (lambda (env)
+       (lambda (e)
+         ((meaning expr) (rename env e var))))]
+    [(exp0 exp1)
+     (lambda (env)
+       (((meaning exp0) env) ((meaning exp1) env)))]
+    [var (lambda (env) (env var))]))
+
+(define (rename env var e)
+  (let ([v (env var)])
+    (lambda (var)
+      (if (eq? e var)
+          v
+          (env var)))))
+
+;; Okay this isn't really that useful
+(define (echo-env)
+  (lambda (x) x))
+(test-begin "echo-env")
+(test-eq 'x ((meaning 'x) (echo-env)))
+(test-eq 'y ((meaning '((lambda (x) x) y)) (echo-env)))
+(test-end "echo-env")
+
+(define (successor-env)
+  (lambda (x)
+    (cond
+     [(number? x) x]
+     [else (lambda (x) (+ x 1))])))
+(test-begin "successor-env")
+(test-eqv 1 ((meaning '(((lambda (f) (lambda (x) (f x))) succ) 0)) (successor-env)))
+(test-eqv 2 ((meaning '(((lambda (f) (lambda (x) (f (f x)))) succ) 0)) (successor-env)))
+(test-end "successor-env")