Macro assertables::assert_lt

source · 
macro_rules! assert_lt {
    ($a:expr, $b:expr $(,)?) => { ... };
    ($a:expr, $b:expr, $($message:tt)+) => { ... };
}
Expand description

Assert a value is less than an expression.

  • If true, return ().

  • Otherwise, call panic! with a message and the values of the expressions with their debug representations.

Examples

// Return Ok
let a = 1;
let b = 2;
assert_lt!(a, b);
//-> ()

let a = 2;
let b = 1;
// Panic with error message
let result = panic::catch_unwind(|| {
assert_lt!(a, b);
//-> panic!
});
assert!(result.is_err());
let actual = result.unwrap_err().downcast::<String>().unwrap().to_string();
let expect = concat!(
    "assertion failed: `assert_lt!(left, right)`\n",
    "  left label: `a`,\n",
    "  left debug: `2`,\n",
    " right label: `b`,\n",
    " right debug: `1`,\n",
    "        left: `2`,\n",
    "       right: `1`"
);
assert_eq!(actual, expect);

// Panic with error message
let result = panic::catch_unwind(|| {
assert_lt!(a, b, "message");
//-> panic!
});
assert!(result.is_err());
let actual = result.unwrap_err().downcast::<String>().unwrap().to_string();
let expect = "message";
assert_eq!(actual, expect);