wrapping_macros

A macro for wrapping arithmetic.

Any code within a wrapping! { .. } block will be transformed as follows:

• a + b becomes a.wrapping_add(b). Similarly for -, *, /, %, <<, >>.
• a += b becomes a = a.wrapping_add(b). Similarly for -=, *=, /=, %=, <<=, >>=.
• -a becomes a.wrapping_neg().

See this Internals thread for the motivation behind this crate.

Note: This crate uses internal compiler APIs, and so requires the Nightly version of Rust.

Cargo

Add this to your Cargo.toml:

wrapping_macros = "*"

Example

#![feature(plugin)]
#![plugin(wrapping_macros)]

fn main() {
    let mut sum = 0u8;
    for x in 0u8..50 {
        wrapping! {
            sum += x;
        }
    }
}

Caveats

• This crate uses unstable APIs, and will only work on Rust Nightly.

• You cannot nest another macro invocation within a wrapping! block. For example, this will not work:

  let x = 41i32;
  wrapping! {
      println!("The answer is {}", x + 1);  //~ ERROR
  }

  Instead, move the macro call out of the block:

  let x = 41i32;
  println!("The answer is {}", wrapping! { x + 1 });