fixed https://github.com/ratfactor/ziglings/issues/156

exercises/064_builtins.zig

@@ -38,14 +38,12 @@ pub fn main() void {
     // Let's try it with a tiny 4-bit integer size to make it clear:
     const a: u4 = 0b1101;
     const b: u4 = 0b0101;
-    var my_result: u4 = undefined;
-    var overflowed: bool = undefined;
-    overflowed = @addWithOverflow(u4, a, b, &my_result);
+    const my_result = @addWithOverflow(a, b);
 
     // Check out our fancy formatting! b:0>4 means, "print
     // as a binary number, zero-pad right-aligned four digits."
     // The print() below will produce: "1101 + 0101 = 0010 (true)".
-    print("{b:0>4} + {b:0>4} = {b:0>4} ({})", .{ a, b, my_result, overflowed });
+    print("{b:0>4} + {b:0>4} = {b:0>4} ({s})", .{ a, b, my_result[0], if (my_result[1] == 1) "true" else "false" });
 
     // Let's make sense of this answer. The value of 'b' in decimal is 5.
     // Let's add 5 to 'a' but go one by one and see where it overflows: