A sample of functional computations in Rust.

functional_squares.rs

// Generates the first 10 odd squares, lazily.
// [1, 9, 25, 49, 81, 121, 169, 225, 289, 361]
// That is, it takes an infinite sequence of squares and 
// checks if each subsequent one is odd, until it finds
// ten that are.
fn main() {
    let vector: Vec<_> = (1..) // Instructions to produce 
                               // integers forever
                               
        .map(|x| x * x) // This is now instructions for 
                        // creating an infinite sequence 
                        // of squares
                        
        .filter(|x| x % 2 != 0) // This is now instructions 
                                // for an infinite sequence 
                                // of _odd_ squares
                                
        .take(10) // This is now instructions to produce a 
                  // sequence of the first 10 odd squares
                  
        .collect(); // Only now does the actual work occur;
                    // the instructions are executed and a
                    // vector is populated with the results.
                    
    println!("{:?}", vector);
}