cryptol/docs/ProgrammingCryptol/enigma/ticket141.cry

/*
 * Copyright (c) 2013-2016 Galois, Inc.
 * Distributed under the terms of the BSD3 license (see LICENSE file)
 */

type Char = [8]
type Permutation = String 26

invSubst : (String 26, Char) -> Char
invSubst (key, c) = candidates ! 0
    where candidates = [0] # [ if c == k then a else p
                             | k <- key
                             | a <- ['A' .. 'Z']
                             | p <- candidates
                             ]