Why false || true is not the same as 0 || 1

Help & Support
1

Hi people, when writing tests I stumbled upon this case

https://play.crystal-lang.org/#/r/ges0

Line 3 outputs true which is ok
But line 4 outpus 0 and I would expect 1

I certainly can understand a short circuit for && but not for ||

What do I miss here ?

2

You miss that 0 is not falsey like other languages. See Truthy and falsey values - Crystal.

2 Likes
3

That’s big surprise ;-)

Mmm it’s causing some problems, I need to find a solution…

1 Like
4

This C code behaves like I want, output is 1

#include <stdio.h>

int main() {
  int a = 0;
  int b = 3;
  int r;

  r = a || b;
  printf("%d", r);
}

How one can mimic this behaviour in Crystal, given that a and b can be any integer values ?
How to write this the line r = a || b; without casting a and b to some Bool

Edit : Answering myself, of course a cast is needed like in

when TypeOperator::AND
          r = (l_lit != 0) && (r_lit != 0)
when TypeOperator::OR
          r = (l_lit != 0) || (r_lit != 0)
5

A possibly more readable version could be:

r = !a.zero? || !b.zero?

Or even:

r = !(a.zero? && b.zero?)

Otherwise, as you’re edit indicates, you’ll need to convert the numbers to bools if you want to treat them like bools.

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