How do I get the minimum or maximum value of an iterator containing floating point numbers?

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Floats have their own min and max methods that handle NaN consistently, so you can fold over the iterator:

use std::f64;

fn main() {
    let x = [2.0, 1.0, -10.0, 5.0, f64::NAN];

    let min = x.iter().fold(f64::INFINITY, |a, &b| a.min(b));
    println!("{}", min);
}

Prints -10.

If you want different NaN handling, you can use PartialOrd::partial_cmp. For example, if you wish to propagate NaNs, fold with:

use std::f64;
use std::cmp::Ordering;

fn main() {
    let x = [2.0, 1.0, -10.0, 5.0, f64::NAN];

    let min = x.iter().fold(f64::INFINITY, |a, &b| {
        match PartialOrd::partial_cmp(&a, &b) {
            None => f64::NAN,
            Some(Ordering::Less) => a,
            Some(_) => b,
        }
    });
    println!("{}", min);
}

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