// 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);
}