Crate eh

Convert values to bool, kind of like C, eh?

Eh roughly follows the implicit conversion rules for C to _Bool or C++ to bool, but Rust requires an explicit conversion. Integer 0, floating-point 0.0, and null pointers are false, and all other values are true.

As a Rust-specific extension, this is also implemented for Option<T> and Result<T, E>. It returns true when the ? operator would unwrap a T value, and false when ? would cause an early return.

Examples

Boolean values just return themselves.

use eh::Eh;
assert!(true.eh());
assert!(true.eh().eh());
assert!(!(false.eh()));

Integers are true for all non-zero values.

use eh::Eh;
use std::i32;
assert!(1.eh());
assert!((-1).eh());
assert!(i32::MIN.eh());
assert!(i32::MAX.eh());
assert!(!(0.eh()));

Wrapping integers follow the same rules.

use eh::Eh;
use std::num::Wrapping;
assert!(Wrapping(1).eh());
assert!(!(Wrapping(0).eh()));

Floats are also true for all non-zero values – including NaN!

use eh::Eh;
use std::f64;
assert!(1.0.eh());
assert!((-1.0).eh());
assert!(f64::EPSILON.eh());
assert!(f64::INFINITY.eh());
assert!(f64::NAN.eh());
assert!(!(0.0.eh()));
assert!(!(-0.0).eh());

Raw pointers are true for any non-null value, without dereferencing.

use eh::Eh;
use std::ptr;
assert!((&0 as *const i32).eh());
assert!((&mut 0 as *mut i32).eh());
assert!(ptr::NonNull::<i32>::dangling().as_ptr().eh());
assert!(!ptr::null::<i32>().eh());
assert!(!ptr::null_mut::<i32>().eh());

Options are true for any Some value, and false for None.

use eh::Eh;
assert!(Some(0).eh());
assert!(Some(1).eh());
assert!(!None::<i32>.eh());

Results are true for any Ok value, and false for any Err value.

use eh::Eh;
assert!(Ok::<i32, i32>(0).eh());
assert!(Ok::<i32, i32>(1).eh());
assert!(!Err::<i32, i32>(0).eh());
assert!(!Err::<i32, i32>(1).eh());

Exclusions

Eh does not implement further boolean conversions of other languages, especially since they’re not universal. For example:

• JavaScript converts NaN to false, different than C and C++ (and eh).
• JavaScript converts empty [] and {} to true, but in Python they’re false.
• Many languages convert empty strings to false and non-empty strings to true, but "0" is also false in Perl and PHP.

About

The name is a play on the Canadian “eh”, turning a declarative sentence into a question.

Traits

Eh

Convert values to bool, kind of like C, eh?