Data update

Task/Gray-code/SETL/gray-code.setl

@@ -0,0 +1,29 @@
+program gray_code;
+    loop for n in [0..31] do
+        print(
+            lpad(str n, 2) + ": " +
+            lpad(bits n, 5) + " => " +
+            lpad(bits(g := gray_encode(n)), 5) + " => " +
+            lpad(bits(d := gray_decode(g)), 5) + ": " +
+            lpad(str d, 2)
+        );
+    end loop;
+
+    proc gray_encode(n);
+        return n bit_xor (n div 2);
+    end proc;
+
+    proc gray_decode(n);
+        loop
+            init r := 0;
+            step n div:= 2;
+            until n=0 do r bit_xor:= n;
+        end loop;
+        return r;
+    end proc;
+
+    op bits(n);
+        b := '' +/ [[str (n mod 2), n div:=2](1) : until n=0];
+        return reverse(b);
+    end op;
+end program;