How to Use std

To hash custom types, implement the std::hash::Hash trait for your struct and combine the hashes of its fields using a std::collections::hash_map::DefaultHasher.

use std::hash::{Hash, Hasher};
use std::collections::hash_map::DefaultHasher;

struct Point {
    x: i32,
    y: i32,
}

impl Hash for Point {
    fn hash<H: Hasher>(&self, state: &mut H) {
        self.x.hash(state);
        self.y.hash(state);
    }
}

This allows your Point struct to be used as a key in std::collections::HashMap.

std::hash tells Rust how to turn your custom data structure into a unique number so it can be stored and found quickly in a hash map. Think of it like creating a unique barcode for a product so a scanner can instantly find its price in a database. Without this, Rust doesn't know how to organize your specific type of data in a lookup table.