Data update

Task/Gray-code/Modula-2/gray-code.mod2

@@ -0,0 +1,57 @@
+MODULE GrayCode;
+
+FROM STextIO IMPORT
+  WriteString, WriteLn;
+FROM SWholeIO IMPORT
+  WriteInt;
+FROM Conversions IMPORT
+  LongBaseToStr;
+FROM FormatString IMPORT
+  FormatString; (* for justifying *)
+
+VAR
+  I, G, D: CARDINAL;
+  Ok: BOOLEAN;
+  BinS, OutBinS: ARRAY[0 .. 5] OF CHAR;
+
+PROCEDURE Encode(V: CARDINAL): CARDINAL;
+BEGIN
+  RETURN V BXOR (V SHR 1)
+END Encode;
+
+PROCEDURE Decode(V: CARDINAL): CARDINAL;
+VAR
+  Result: CARDINAL;
+BEGIN
+  Result := 0;
+  WHILE V > 0 DO
+    Result := Result BXOR V;
+    V := V SHR 1
+  END;
+  RETURN Result
+END Decode;
+
+BEGIN
+  WriteString("decimal  binary   gray    decoded");
+  WriteLn;
+  FOR I := 0 TO 31 DO
+    G := Encode(I);
+    D := Decode(G);
+    WriteInt(I, 4);
+    WriteString("     ");
+    Ok := LongBaseToStr(I, 2, BinS);
+    Ok := FormatString("%'05s", OutBinS, BinS);
+    (* Padded with 0; width: 5; type: string *)
+    WriteString(OutBinS);
+    WriteString("   ");
+    Ok := LongBaseToStr(G, 2, BinS);
+    Ok := FormatString("%'05s", OutBinS, BinS);
+    WriteString(OutBinS);
+    WriteString("   ");
+    Ok := LongBaseToStr(D, 2, BinS);
+    Ok := FormatString("%'05s", OutBinS, BinS);
+    WriteString(OutBinS);
+    WriteInt(D, 4);
+    WriteLn;
+  END
+END GrayCode.