Macro assert_exists

macro_rules! assert_exists {
    ($iter:expr, $pred:expr) => { ... };
    ($iter:expr, $pred:expr, $($msg:tt)+) => { ... };
}

Asserts that at least one element satisfies the predicate.

Example

use quantor::assert_exists;
 
let numbers = vec!(0, 1, 3, 5);
 
assert_exists!(&numbers, |x| x % 2 == 0);