Generic functions and bounds in Rust

A type parameter with bounds: one function, every type that satisfies the trait.

fn biggest<T: PartialOrd + Copy>(values: &[T]) -> T {
    let mut best = values[0];
    for v in values {
        if *v > best {
            best = *v;
        }
    }
    best
}

fn describe<T>(value: T) -> String
where
    T: std::fmt::Debug + Clone,
{
    format!("{:?}", value.clone())
}

fn main() {
    println!("{}", biggest(&[3, 9, 2]));
    println!("{}", biggest(&[1.5, 0.5]));
    println!("{}", describe(vec![1, 2]));
}

How it works

1. <T: PartialOrd> says T must be comparable.
2. A where clause carries longer bound lists off the signature.
3. Monomorphisation compiles one copy per concrete type.

Keywords and builtins used here

• Clone
• Copy
• PartialOrd
• String
• T
• biggest
• describe
• fn
• for
• if
• in
• let
• main
• mut
• std
• where

The run, in numbers

Lines

22

Characters to type

367

Tokens

145

Three-star pace

105 tpm

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Type this snippet

Step 1 of 4 in Generics, step 4 of 19 in Traits & generics.

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