Closures are a type of anonymous function that can capture variables from their surrounding environment, and create self-contained units of behavior that can be passed around and reused.
Example of a closure in Rust:
let add = |a, b| a + b;
let result = add(3, 4);In this example, we define a closure add that takes a and b and returns their sum. We call the closure with 3 and 4 and print the result.
Closures in Rust are defined using the | symbol to specify the arguments, followed by the body in braces {}. Rust's type inference system allows you to omit the types of the arguments, if they can be inferred.
Example of a closure that accesses a variable outside of it:
let x = 5;
let add_x = |y| x + y;
let result = add_x(3);In this example, we define a closure add_x that takes an argument y and adds it to the variable x that is already defined outside of the closure. When we call the closure with argument 3, it captures the value of x and returns 8.
Example of a closure for collection iterator map function:
let numbers = vec![1, 2, 3, 4];
let squares = numbers.iter().map(|x| x * x);In this example, we define a vector of numbers, then use the iter method to create an iterator over the vector's elements. We then use the map method to apply a closure that squares each element of the vector.