Data commit

Task/Caesar-cipher/Prolog/caesar-cipher.pro

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+:- use_module(library(clpfd)).
+
+caesar :-
+	L1 = "The five boxing wizards jump quickly",
+	writef("Original : %s\n", [L1]),
+
+	% encryption of the sentence
+	encoding(3, L1, L2) ,
+	writef("Encoding : %s\n", [L2]),
+
+	% deciphering on the encoded sentence
+	encoding(3, L3, L2),
+	writef("Decoding : %s\n", [L3]).
+
+% encoding/decoding of a sentence
+encoding(Key, L1, L2) :-
+	maplist(caesar_cipher(Key), L1, L2).
+
+caesar_cipher(_, 32, 32) :- !.
+
+caesar_cipher(Key, V1, V2) :-
+	V #= Key + V1,
+
+	% we verify that we are in the limits of A-Z and a-z.
+	((V1 #=< 0'Z #/\ V #> 0'Z) #\/ (V1 #=< 0'z #/\ V #> 0'z)
+	#\/
+	(V1 #< 0'A #/\ V2 #>= 0'A)#\/ (V1 #< 0'a #/\ V2 #>= 0'a)) #==> A,
+
+	% if we are not in these limits A is 1, otherwise 0.
+	V2 #= V - A * 26,
+
+	% compute values of V1 and V2
+	label([A, V1, V2]).