Sync

Task/Gray-code/Component-Pascal/gray-code.component

@@ -0,0 +1,51 @@
+MODULE GrayCodes;
+IMPORT StdLog,SYSTEM;
+
+PROCEDURE Encode*(i: INTEGER; OUT x: INTEGER);
+VAR
+	j: INTEGER;
+	s,r: SET;
+BEGIN
+	s := BITS(i);j := MAX(SET);
+	WHILE (j >= 0) & ~(j IN s) DO DEC(j) END;
+	r := {};IF j >= 0 THEN INCL(r,j) END;
+	WHILE j > 0 DO
+		IF ((j IN s) & ~(j - 1 IN s)) OR (~(j IN s) & (j - 1 IN s)) THEN INCL(r,j-1) END;
+		DEC(j)
+	END;
+	x := SYSTEM.VAL(INTEGER,r)
+END Encode;
+
+PROCEDURE Decode*(x: INTEGER; OUT i: INTEGER);
+VAR
+	j: INTEGER;
+	s,r: SET;
+BEGIN
+	s := BITS(x);r:={};j := MAX(SET);
+	WHILE (j >= 0) & ~(j IN s) DO DEC(j) END;
+	IF j >= 0 THEN INCL(r,j) END;
+	WHILE j > 0 DO
+		IF ((j IN r) & ~(j - 1 IN s)) OR (~(j IN r) & (j - 1 IN s)) THEN INCL(r,j-1) END;
+		DEC(j)
+	END;
+	i := SYSTEM.VAL(INTEGER,r);
+END Decode;
+
+
+PROCEDURE Do*;
+VAR
+	grayCode,binCode: INTEGER;
+	i: INTEGER;
+BEGIN
+	StdLog.String(" i ");StdLog.String("     bin code    ");StdLog.String("   gray code    ");StdLog.Ln;
+	StdLog.String("---");StdLog.String(" ----------------");StdLog.String(" ---------------");StdLog.Ln;
+	FOR i := 0 TO 32 DO;
+		Encode(i,grayCode);Decode(grayCode,binCode);
+		StdLog.IntForm(i,10,3,' ',FALSE);
+		StdLog.IntForm(binCode,2,16,' ',TRUE);
+		StdLog.IntForm(grayCode,2,16,' ',TRUE);
+		StdLog.Ln;
+	END
+END Do;
+
+END GrayCodes.

Task/Gray-code/D/gray-code-3.d

@@ -1,11 +1,11 @@
 import std.stdio, std.algorithm, std.range;
 
-string[] g(in uint n) /*pure nothrow*/ {
-    return n ? g(n - 1).map!q{'0' ~ a}().array() ~
-               g(n - 1).retro().map!q{'1' ~ a}().array()
+string[] g(in uint n) pure nothrow {
+    return n ? g(n - 1).map!q{'0' ~ a}.array ~
+               g(n - 1).retro.map!q{'1' ~ a}.array
              : [""];
 }
 
 void main() {
-    writeln(g(4));
+    4.g.writeln;
 }

Task/Gray-code/Icon/gray-code.icon

@@ -0,0 +1,18 @@
+link bitint
+
+procedure main()
+    every write(right(i := 0 to 10,4),":",right(int2bit(i),10)," -> ",
+                                          right(g := gEncode(i),10)," -> ",
+                                          right(b := gDecode(g),10)," -> ",
+                                          right(bit2int(b),10))
+end
+
+procedure gEncode(b)
+    return int2bit(ixor(b, ishift(b,-1)))
+end
+
+procedure gDecode(g)
+    b := g[1]
+    every i := 2 to *g do b ||:= if g[i] == b[i-1] then "0" else "1"
+    return b
+end

Task/Gray-code/Mercury/gray-code-1.mercury

@@ -0,0 +1,30 @@
+:- module gray.
+
+:- interface.
+:- import_module int.
+
+:- type gray.
+
+% VALUE conversion functions
+:- func gray.from_int(int) = gray.
+:- func gray.to_int(gray) = int.
+
+% REPRESENTATION conversion predicate
+:- pred gray.coerce(gray, int).
+:- mode gray.coerce(in,   out) is det.
+:- mode gray.coerce(out,  in)  is det.
+
+:- implementation.
+
+:- import_module list.
+
+:- type gray
+  ---> gray(int).
+
+gray.from_int(X) = gray(X `xor` (X >> 1)).
+
+gray.to_int(gray(G)) = (G > 0 -> G `xor` gray.to_int(gray(G >> 1))
+                        ;        G).
+gray.coerce(gray(I), I).
+
+:- end_module gray.

Task/Gray-code/Mercury/gray-code-2.mercury

@@ -0,0 +1,40 @@
+:- module gray_test.
+
+:- interface.
+
+:- import_module io.
+
+:- pred main(io::di, io::uo) is det.
+
+:- implementation.
+
+:- import_module gray.
+:- import_module int, list, string.
+
+:- pred check_conversion(list(int)::in, list(gray)::out) is semidet.
+:- pred display_lists(list(int)::in, list(gray)::in, io::di, io::uo) is det.
+:- pred display_record(int::in, gray::in, io::di, io::uo) is det.
+
+main(!IO) :-
+  Numbers = 0..31,
+  ( check_conversion(Numbers, Grays) ->
+      io.format("%8s %8s %8s\n", [s("Number"), s("Binary"), s("Gray")], !IO),
+      io.format("%8s %8s %8s\n", [s("------"), s("------"), s("----")], !IO),
+      display_lists(Numbers, Grays, !IO)
+
+  ;   io.write("Either conversion or back-conversion failed.\n", !IO)).
+
+check_conversion(Numbers, Grays) :-
+  Grays = list.map(gray.from_int, Numbers),
+  Numbers = list.map(gray.to_int, Grays).
+
+display_lists(Numbers, Grays, !IO) :-
+  list.foldl_corresponding(display_record, Numbers, Grays, !IO).
+
+display_record(Number, Gray, !IO) :-
+  gray.coerce(Gray, GrayRep),
+  NumBin = string.int_to_base_string(Number, 2),
+  GrayBin = string.int_to_base_string(GrayRep, 2),
+  io.format("%8d %8s %8s\n", [i(Number), s(NumBin), s(GrayBin)], !IO).
+
+:- end_module gray_test.

Task/Gray-code/PHP/gray-code.php

@@ -0,0 +1,28 @@
+<?php
+
+/**
+ * @author Elad Yosifon
+ */
+
+/**
+ * @param int $binary
+ * @return int
+ */
+function gray_encode($binary){
+	return $binary ^ ($binary >> 1);
+}
+
+/**
+ * @param int $gray
+ * @return int
+ */
+function gray_decode($gray){
+	$binary = $gray;
+	while($gray >>= 1) $binary ^= $gray;
+	return $binary;
+}
+
+for($i=0;$i<32;$i++){
+	$gray_encoded = gray_encode($i);
+	printf("%2d : %05b => %05b => %05b : %2d \n",$i, $i, $gray_encoded, $gray_encoded, gray_decode($gray_encoded));
+}

Task/Gray-code/Prolog/gray-code-1.pro

@@ -0,0 +1,10 @@
+to_gray(N, G) :-
+  N0 is N >> 1,
+  G is N xor N0.
+
+from_gray(G, N) :-
+  ( G > 0
+  ->  S is G >> 1,
+      from_gray(S, N0),
+      N is G xor N0
+  ;   N is G ).

Task/Gray-code/Prolog/gray-code-2.pro

@@ -0,0 +1,31 @@
+:- use_module(library(apply)).
+
+to_gray(N, G) :-
+  N0 is N >> 1,
+  G is N xor N0.
+
+from_gray(G, N) :-
+  ( G > 0
+  ->  S is G >> 1,
+      from_gray(S, N0),
+      N is G xor N0
+  ;   N is G ).
+
+make_num(In, Out) :-
+  atom_to_term(In, Out, _),
+  integer(Out).
+
+write_record(Number, Gray, Decoded) :-
+  format('~w~10|~2r~10+~2r~10+~2r~10+~w~n',
+         [Number, Number, Gray, Decoded, Decoded]).
+
+go :-
+  setof(N, between(0, 31, N), Numbers),
+  maplist(to_gray, Numbers, Grays),
+  maplist(from_gray, Grays, Decodeds),
+  format('~w~10|~w~10+~w~10+~w~10+~w~n',
+         ['Number', 'Binary', 'Gray', 'Decoded', 'Number']),
+  format('~w~10|~w~10+~w~10+~w~10+~w~n',
+         ['------', '------', '----', '-------', '------']),
+  maplist(write_record, Numbers, Grays, Decodeds).
+go :- halt(1).