Language: C C++ D Haskell Lua OCaml PHP Perl Plain Text Python Ruby Scheme Tcl ; affine-shift cipher (define (inverse x n) (let loop ((x (modulo x n)) (a 1)) (cond ((zero? x) (return #f)) ((= x 1) a) (else (let ((q (- (quotient n x)))) (loop (+ n (* q x)) (modulo (* q a) n))))))) (define (c->int c) (- (char->integer c) 65)) (define (int->c i) (integer->char (+ i 65))) (define (cipher a b) (lambda (x) (modulo (+ (* a x) b) 26))) (define (plain a b) (lambda (x) (modulo (* (inverse a 26) (- x b)) 26))) (define (mapping func text) (list->string (map int->c (map func (map c->int (string->list text)))))) (define (encipher a b text) (mapping (cipher a b) text)) (define (decipher a b text) (mapping (plain a b) text)) (display (encipher 5 8 "PROGRAMMINGPRAXIS")) (newline) (display (decipher 5 8 "FPAMPIQQWVMFPITWU")) (newline) Private [?] Run code