Hi!
While solving an exercise, I was sad to learn that in zig @intFromBool() returns a type u1 which meant I couldn’t chain them together:
fn equalSidesCount(self: Triangle) u8 {
return @intFromBool(self.a == self.b) +
@intFromBool(self.a == self.c) +
@intFromBool(self.b == self.c);
}
$ zig test test_triangle.zig
thread 27344997 panic: integer overflow
/path/to/triangle.zig:10:47: 0x102c36d0f in equalSidesCount (test)
return @intFromBool(self.a == self.b) +
@intFromBool(self.a == self.c) +
@intFromBool(self.b == self.c);
So I worked around that limitation by wrapping them all inside a @as(u8).
fn equalSidesCount(self: Triangle) u8 {
return @as(u8, @intFromBool(self.a == self.b)) +
@as(u8, @intFromBool(self.a == self.c)) +
@as(u8, @intFromBool(self.b == self.c));
}
This solution worked but it looked a bit too verbose. I submitted it and since I couldn’t afford mentors anymore with my reputation, I went to ask on zig’s official IRC channel if there was a better way.
torque | you only need to wrap one of them in the @as(u8)
torque | the rest will be promoted
Great news! I updated my answer:
fn equalSidesCount(self: Triangle) u8 {
return @as(u8, @intFromBool(self.a == self.b)) +
@intFromBool(self.a == self.c) +
@intFromBool(self.b == self.c);
}
And tested locally:
$ zig test test_triangle.zig
All 21 tests passed.
Great! It worked! So I re-submitted my answer.
Only on Exercism’s server, it didn’t compile. Ok no panic, let’s look at the compiler’s error message:
triangle.zig:10:24: error: invalid builtin function: '@intFromBool'
return @as(u8, @intFromBool(self.a == self.b)) +
@intFromBool(self.a == self.c) +
@intFromBool(self.b == self.c);
How come? @intFromBool() worked for my first iteration when it was wrapped inside @as(), just by removing @as() it stops being a valid builtin? That has to be a bug, right?
(BTW, I have zig 0.13.0 on a Mac)
