Data commit

Task/Truth-table/Racket/truth-table.rkt

@@ -0,0 +1,28 @@
+#lang racket
+
+(define (collect-vars sexpr)
+  (sort
+   (remove-duplicates
+    (let loop ([x sexpr])
+      (cond [(boolean? x) '()]
+            [(symbol? x) (list x)]
+            [(list? x) (append-map loop (cdr x))]
+            [else (error 'truth-table "Bad expression: ~e" x)])))
+   string<? #:key symbol->string))
+
+(define ns (make-base-namespace))
+
+(define (truth-table sexpr)
+  (define vars (collect-vars sexpr))
+  (printf "~a => ~s\n" (string-join (map symbol->string vars)) sexpr)
+  (for ([i (expt 2 (length vars))])
+    (define vals
+      (map (λ(x) (eq? #\1 x))
+           (reverse (string->list (~r i #:min-width (length vars)
+                                        #:pad-string "0"
+                                        #:base 2)))))
+    (printf "~a => ~a\n" (string-join (map (λ(b) (if b "T" "F")) vals))
+            (if (eval `(let (,@(map list vars vals)) ,sexpr) ns) "T" "F"))))
+
+(printf "Enter an expression: ")
+(truth-table (read))