Macro const_format::unwrap_or_else

macro_rules! unwrap_or_else {
    ($e:expr, |$($error:ident)? $(_)*| $orelse:expr ) => { ... };
}

This is supported on crate feature fmt only.

Equivalent to Result::unwrap_or_else but allows returning from the enclosing function.

Examples

Early return

#![feature(const_mut_refs)]

use const_format::unwrap_or_else;

const fn unwrap_square(number: Result<u32, u32>) -> u64 {
    let n = unwrap_or_else!(number, |n| return n as u64 ) as u64;
    n * n
}

assert_eq!(unwrap_square(Ok(10)), 100);
assert_eq!(unwrap_square(Ok(30)), 900);
assert_eq!(unwrap_square(Err(100)), 100);

As unwrap_or

#![feature(const_mut_refs)]

use const_format::{AsciiStr, strwriter_as_str, unwrap_or_else};

const FOO: AsciiStr = unwrap_or_else!(AsciiStr::new(b"AB\x80"), |_| AsciiStr::empty() );

const BAR: AsciiStr = unwrap_or_else!(AsciiStr::new(b"bar"), |_| loop{} );

assert_eq!(FOO.as_str(), "");
assert_eq!(BAR.as_str(), "bar");