Add final questions

2025-04-23 17:10:17 -03:00
parent 81c8032091
commit 6a7e549304
3 changed files with 742 additions and 0 deletions
--- a/Final/1.rkt
+++ b/Final/1.rkt
@ -0,0 +1,112 @@
+#lang plait
+(define-type Exp
+  [numE (val : Number)]
+  [plusE (l : Exp) (r : Exp)]
+  [varE (name : Symbol)]
+  [let1E (id : Symbol) (named-expr : Exp) (bound-body : Exp)]
+  [lamE (param : Symbol) (body : Exp)]
+  [callWith (id : Symbol) (bound-expr : Exp) (fun : Exp) (val : Exp)]
+  [appE (fun : Exp) (val : Exp)])
+
+(define-type Value
+  [numV (n : Number)]
+  [lamV (arg : Symbol) (body : Exp) (env : Env)])
+
+(define-type-alias Env (Hashof Symbol Value))
+(define mt-env (hash empty)) ;; "empty environment"
+
+(define (lookup (s : Symbol) (n : Env))
+  (type-case (Optionof Value) (hash-ref n s)
+    [(none) (error s "not bound")]
+    [(some v) v]))
+
+(define (extend old-env new-name value)
+  (hash-set old-env new-name value))
+
+(define (interp expr env)
+  (type-case Exp expr
+    [(numE n) (numV n)]
+    [(plusE l r)
+     (numV (+ (numV-n (interp l env)) (numV-n (interp r env))))]
+    [(let1E bound-id named-expr bound-body)
+     (interp bound-body (extend env bound-id (interp named-expr env)))]
+    [(varE name) (lookup name env)]
+    [(lamE bound-id bound-body) (lamV bound-id bound-body env)]
+    [(callWith with-id with-expr fun-expr arg-expr) ....]
+    [(appE fun-expr arg-expr)
+     (let ([fval (interp fun-expr env)])
+       (type-case Value fval
+         [(lamV bound-id bound-body f-env)
+          (interp bound-body
+                  (extend f-env bound-id (interp arg-expr env)))]
+         [else (error 'interp
+                      (string-append "`call' expects a function, got: "
+                                     (to-string fval)))]))]))
+
+(module+ test
+  (print-only-errors #t)
+  (define (example body)
+    (let1E 'x (numE 3)
+           (let1E 'f (lamE 'y (plusE (varE 'x) (varE 'y)))
+                  body)))
+
+
+  (test (interp (example (appE (varE 'f) (numE 4))) mt-env)
+        (numV 7))
+
+  (test (interp
+         (example (callWith 'x (numE 5) (varE 'f) (numE 4))) mt-env)
+        (numV 9))
+
+  (test (interp
+         (example
+          (let1E 'f (lamE 'x (varE 'x))
+                 (callWith 'x (numE 5) (varE 'f) (numE 4))))
+         mt-env)
+        (numV 4))
+
+  (test (interp
+         (example
+          (let1E 'f (lamE 'y (varE 'x))
+                 (callWith 'x (numE 5) (varE 'f) (numE 4))))
+         mt-env)
+        (numV 5))
+
+  (test
+   (interp (callWith 'y (numE 7) (lamE 'x  (plusE (varE 'x) (varE 'y))) (numE 3))
+           mt-env)
+   (numV 10))
+  
+  (test/exn
+   (interp (callWith 'x (numE 7) (lamE 'x  (plusE (varE 'x) (varE 'y))) (numE 3))
+           mt-env)
+   "not bound")
+
+  (test
+   (interp 
+    (callWith 'x (numE 7) (lamE 'x  (plusE (varE 'x) (varE 'x))) (numE 3))
+    mt-env)
+   (numV 6))
+
+  (test
+   (interp
+    (let1E 'z (numE 7)
+           (callWith 'y (varE 'z) (lamE 'x  (plusE (varE 'x) (varE 'y))) (numE 3)))
+    mt-env)
+   (numV 10))
+  (test
+   (interp
+    (let1E 'f (lamE 'x  (plusE (varE 'x) (varE 'y)))
+           (callWith 'y (numE 7) (varE 'f) (numE 3)))
+    mt-env)
+   (numV 10))
+  (test
+   (interp
+    (let1E 'f  (lamE 'x  (plusE (varE 'x) (varE 'y)))
+           (let1E 'z (numE 7) (callWith 'y (varE 'z) (varE 'f) (numE 3))))
+    mt-env)
+   (numV 10))
+
+  (test/exn (interp (appE (varE 'g) (numE 4)) mt-env) "not bound")
+  (test/exn (interp (example (appE (numE 4) (varE 'f))) mt-env) "function")
+  (test/exn (interp (example (callWith 'x (numE 5) (numE 4) (varE 'f))) mt-env) "function"))