step

step is a crate that provides the trait Step, which allows for unit steps and arbitrary steps on numeric types.

Documentation can be found on docs.rs.

Using step

Add the crate to the dependencies section of Cargo.toml:

[dependencies]
step = { git = "https://github.com/ryanq/step" }

Then import the crate and type in your source:

extern crate step;

use step::Step;

Then you can use the functions for incrementing and decrementing numbers or implement it on your own types:

let number = 42;

assert_eq!(number.next(), 43);
assert_eq!(number.next_by(&3), 45);
assert_eq!(number.prev(), 41);
assert_eq!(number.prev_by(&3), 39);

struct Foo {
    bar: i32,
}

impl Step for Foo {
    fn next(&self) -> Self { Foo { bar: self.bar + 1 } }
    fn next_by(&self, by: &Self) -> Self { Foo { bar: self.bar + *by } }
    fn prev(&self) -> Self { Foo { bar: self.bar - 1 } }
    fn prev_by(&self, by: &Self) -> Self { Foo { bar: self.bar - *by } }
}