# core::assert!
[−]
[src]

macro_rules! assert { ($cond:expr) => { ... }; ($cond:expr, $($arg:tt)+) => { ... }; }

Ensure that a boolean expression is `true`

at runtime.

This will invoke the `panic!`

macro if the provided expression cannot be
evaluated to `true`

at runtime.

This macro has a second version, where a custom panic message can be provided.

# Examples

fn main() { // the panic message for these assertions is the stringified value of the // expression given. assert!(true); fn some_computation() -> bool { true } // a very simple function assert!(some_computation()); // assert with a custom message let x = true; assert!(x, "x wasn't true!"); let a = 3; let b = 27; assert!(a + b == 30, "a = {}, b = {}", a, b); }// the panic message for these assertions is the stringified value of the // expression given. assert!(true); fn some_computation() -> bool { true } // a very simple function assert!(some_computation()); // assert with a custom message let x = true; assert!(x, "x wasn't true!"); let a = 3; let b = 27; assert!(a + b == 30, "a = {}, b = {}", a, b);