duplicate

Crate for easy code duplication with substitution.

Motivation

If you find yourself in need of copying a block of code and then making some small changes to fit the new use case, this crate is for you.

The duplicate attribute macro will duplicate an item any number of times while inserting custom code in the designated places in each duplicate. The duplicate_inline function-like procedural macro will do the same for any code you give it.

For an in-depth explanation of the syntax and features, see the documentation.

Example

use duplicate::duplicate;

/// Trait we want to implement for u8, u16, and u32
trait IsMax {
  /// Returns true if self is its maximum possible value.
  fn is_max(&self) -> bool;
}

#[duplicate(
  int_type  max_value;
  [ u8 ]    [ 255 ];
  [ u16 ]   [ 65_535 ];
  [ u32 ]   [ 4_294_967_295 ];
)]
impl IsMax for int_type {
  fn is_max(&self) -> bool {
    *self == max_value
  }
}

assert!(!42u8.is_max());
assert!(!42u16.is_max());
assert!(!42u32.is_max());

Expands to:

use duplicate::duplicate;

/// Trait we want to implement for u8, u16, and u32
trait IsMax {
  /// Returns true if self is its maximum possible value.
  fn is_max(&self) -> bool;
}

impl IsMax for u8 {
  fn is_max(&self) -> bool {
    *self == 255
  }
}
impl IsMax for u16 {
  fn is_max(&self) -> bool {
    *self == 65_535
  }
}
impl IsMax for u32 {
  fn is_max(&self) -> bool {
    *self == 4_294_967_295
  }
}

assert!(!42u8.is_max());
assert!(!42u16.is_max());
assert!(!42u32.is_max());

Changelog

This project adheres to Semantic Versioning. During initial development (with versions 0.y.z), bumps to the minor version (y) signify breaking changes.

Added

• duplicate_inline: Function-like procedural macro version of duplicate. Has the same functionality, but can be used in other contexts and can duplicate any number of items. See also #6.

This changelog format is based on Keep a Changelog and shows only the changes since the previous version. See the full changelog for changes to all released versions.

License