create a closure in rust

In Rust, a closure is an anonymous function that can capture variables from its surrounding environment. To create a closure, we use the |args| body syntax, where args is the list of arguments for the closure, and body is the code that the closure executes.

Here's an example of a closure that adds two numbers together:

main.rs
let sum = |a, b| a + b;
let result = sum(4, 5); // result is 9
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In this example, we defined a closure called sum that takes two arguments a and b, and returns their sum. We then called this closure with the arguments 4 and 5, and assigned the result to the variable result.

Closures can also capture variables from their surrounding environment. This is done using the move keyword, like this:

main.rs
let x = 1;
let square_x = move || x * x;
let result = square_x(); // result is 1
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In this example, we defined a closure called square_x that captures the variable x from its surrounding environment. We then called this closure with no arguments, and assigned the result to the variable result. Since x was captured by value (using the move keyword), we can still access it even though it's outside the closure's scope.