Generic structs in Rust

A struct over a type parameter, with impl blocks that can be generic or specific.

struct Pair<T> {
    left: T,
    right: T,
}

impl<T> Pair<T> {
    fn new(left: T, right: T) -> Self {
        Pair { left, right }
    }
}

impl<T: PartialOrd + std::fmt::Display> Pair<T> {
    fn larger(&self) -> &T {
        if self.left > self.right {
            &self.left
        } else {
            &self.right
        }
    }
}

fn main() {
    let nums = Pair::new(7, 12);
    println!("{}", nums.larger());
    println!("{}", Pair::new("fig", "apple").larger());
}

How it works

1. The parameter is declared on both the struct and the impl.
2. A second impl block can target one concrete type only.
3. Methods may add bounds the struct itself does not need.

Keywords and builtins used here

• Pair
• PartialOrd
• Self
• T
• else
• fn
• if
• impl
• larger
• let
• main
• new
• self
• struct

The run, in numbers

Lines

26

Characters to type

386

Tokens

151

Three-star pace

105 tpm

At the three-star pace of 105 tokens a minute, this run takes about 86 seconds.

Type this snippet

Step 3 of 4 in Generics, step 6 of 19 in Traits & generics.

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