How to make a reverse ordered for loop in Rust?

Question

Editor\'s note: This question was asked before Rust 1.0 was released and the .. \"range\" operator was introduced. The question\'s code no longer

Answer 1

Editor's note: This question refers to parts of Rust that predate Rust 1.0. Look at other answers for up to date code.

Your code doesn't work because a uint of value -1 is equal the maximum value of uint. The range_step iterator stops immediately upon detecting overflow. Using an int fixes this.

std::iter::range_step(100i, 0, -1)

You can also reverse an iterator with rev().

for n in range(0u, 100).rev() { ... }

Though note that this will be from 99->0, rather than 100->1.

Answer 2

A forward loop is like this:

for x in 0..100 {
    println!("{}", x);
}

And a reverse loop is done by calling Iterator::rev to reverse the order:

for x in (0..100).rev() {
    println!("{}", x);
}