Required Methods

fn total_cmp(self: &Self, other: &Self) -> Ordering

Return the ordering between self and other.

Unlike the standard partial comparison between floating point numbers, this comparison always produces an ordering in accordance to the totalOrder predicate as defined in the IEEE 754 (2008 revision) floating point standard. The values are ordered in the following sequence:

• negative quiet NaN
• negative signaling NaN
• negative infinity
• negative numbers
• negative subnormal numbers
• negative zero
• positive zero
• positive subnormal numbers
• positive numbers
• positive infinity
• positive signaling NaN
• positive quiet NaN.

The ordering established by this function does not always agree with the PartialOrd and PartialEq implementations. For example, they consider negative and positive zero equal, while total_cmp doesn't.

The interpretation of the signaling NaN bit follows the definition in the IEEE 754 standard, which may not match the interpretation by some of the older, non-conformant (e.g. MIPS) hardware implementations.

Examples

use num_traits::float::TotalOrder;
use std::cmp::Ordering;
use std::{f32, f64};

fn check_eq<T: TotalOrder>(x: T, y: T) {
    assert_eq!(x.total_cmp(&y), Ordering::Equal);
}

check_eq(f64::NAN, f64::NAN);
check_eq(f32::NAN, f32::NAN);

fn check_lt<T: TotalOrder>(x: T, y: T) {
    assert_eq!(x.total_cmp(&y), Ordering::Less);
}

check_lt(-f64::NAN, f64::NAN);
check_lt(f64::INFINITY, f64::NAN);
check_lt(-0.0_f64, 0.0_f64);