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//! Provides a macro to simplify operator overloading.
//!
//! To use, include the following:
//! ```
//! extern crate overload;
//! use overload::overload;
//! use std::ops; // <- don't forget this or you'll get nasty errors
//! ```
//!
//! # Introduction
//!
//! Suppose we have the following `struct` definition:
//! ```
//! #[derive(PartialEq, Debug)]
//! struct Val {
//! v: i32
//! }
//! ```
//! We can overload the addition of `Val`s like so:
//! ```
//! # extern crate overload;
//! # use overload::overload;
//! # use std::ops;
//! # #[derive(PartialEq, Debug)]
//! # struct Val {
//! # v: i32
//! # }
//! overload!((a: Val) + (b: Val) -> Val { Val { v: a.v + b.v } });
//! ```
//! The macro call above generates the following code:
//! ```ignore
//! impl ops::Add<Val> for Val {
//! type Output = Val;
//! fn add(self, b: Val) -> Self::Output {
//! let a = self;
//! Val { v: a.v + b.v }
//! }
//! }
//! ```
//! We are now able to add `Val`s:
//! ```
//! # extern crate overload;
//! # use overload::overload;
//! # use std::ops;
//! # #[derive(PartialEq, Debug)]
//! # struct Val {
//! # v: i32
//! # }
//! # overload!((a: Val) + (b: Val) -> Val { Val { v: a.v + b.v } });
//! assert_eq!(Val{v:3} + Val{v:5}, Val{v:8});
//! ```
//!
//! # Owned and borrowed types
//!
//! If we also wanted to overload addition for the borrowed type `&Val` we could write:
//! ```
//! # extern crate overload;
//! # use overload::overload;
//! # use std::ops;
//! # #[derive(PartialEq, Debug)]
//! # struct Val {
//! # v: i32
//! # }
//! overload!((a: &Val) + (b: &Val) -> Val { Val { v: a.v + b.v } });
//! ```
//! We might also want to overload addition between the owned and borrowed types:
//! ```
//! # extern crate overload;
//! # use overload::overload;
//! # use std::ops;
//! # #[derive(PartialEq, Debug)]
//! # struct Val {
//! # v: i32
//! # }
//! overload!((a: Val) + (b: &Val) -> Val { Val { v: a.v + b.v } });
//! overload!((a: &Val) + (b: Val) -> Val { Val { v: a.v + b.v } });
//! ```
//! Let's see how we can write these combinations more concisely.
//!
//! We can include a `?` in front of a type to indicate that it should stand in for both the owned and borrowed type.
//!
//! To overload addition for all four combinations between `Val` and `&Val` we can therefore simply include a `?` in front of both types:
//! ```
//! # extern crate overload;
//! # use overload::overload;
//! # use std::ops;
//! # #[derive(PartialEq, Debug)]
//! # struct Val {
//! # v: i32
//! # }
//! overload!((a: ?Val) + (b: ?Val) -> Val { Val { v: a.v + b.v } });
//! ```
//! The macro call above generates the following code:
//! ```ignore
//! impl ops::Add<Val> for Val {
//! type Output = Val;
//! fn add(self, b: Val) -> Self::Output {
//! let a = self;
//! Val { v: a.v + b.v }
//! }
//! }
//!
//! impl ops::Add<&Val> for Val {
//! type Output = Val;
//! fn add(self, b: &Val) -> Self::Output {
//! let a = self;
//! Val { v: a.v + b.v }
//! }
//! }
//!
//! impl ops::Add<Val> for &Val {
//! type Output = Val;
//! fn add(self, b: Val) -> Self::Output {
//! let a = self;
//! Val { v: a.v + b.v }
//! }
//! }
//!
//! impl ops::Add<&Val> for &Val {
//! type Output = Val;
//! fn add(self, b: &Val) -> Self::Output {
//! let a = self;
//! Val { v: a.v + b.v }
//! }
//! }
//! ```
//! We are now able to add `Val`s and `&Val`s in any combination:
//! ```
//! # extern crate overload;
//! # use overload::overload;
//! # use std::ops;
//! # #[derive(PartialEq, Debug)]
//! # struct Val {
//! # v: i32
//! # }
//! # overload!((a: ?Val) + (b: ?Val) -> Val { Val { v: a.v + b.v } });
//! assert_eq!(Val{v:3} + Val{v:5}, Val{v:8});
//! assert_eq!(Val{v:3} + &Val{v:5}, Val{v:8});
//! assert_eq!(&Val{v:3} + Val{v:5}, Val{v:8});
//! assert_eq!(&Val{v:3} + &Val{v:5}, Val{v:8});
//! ```
//!
//! # Binary operators
//!
//! The general syntax to overload a binary operator between types `<a_type>` and `<b_type>` is:
//! ```ignore
//! overload!((<a_ident>: <a_type>) <op> (<b_ident>: <b_type>) -> <out_type> { /*body*/ });
//! ```
//! Inside the body you can use `<a_ident>` and `<b_ident>` freely to perform any computation.
//!
//! The last line of the body needs to be an expression (i.e. no `;` at the end of the line) of type `<out_type>`.
//!
//! | Operator | Example | Trait |
//! |----------|-----------------------------------------------------------------|--------|
//! | + | `overload!((a: A) + (b: B) -> C { /*...*/ );` | Add |
//! | - | `overload!((a: A) - (b: B) -> C { /*...*/ );` | Sub |
//! | * | `overload!((a: A) * (b: B) -> C { /*...*/ );` | Mul |
//! | / | `overload!((a: A) / (b: B) -> C { /*...*/ );` | Div |
//! | % | `overload!((a: A) % (b: B) -> C { /*...*/ );` | Rem |
//! | & | `overload!((a: A) & (b: B) -> C { /*...*/ );` | BitAnd |
//! | \| | <code>overload!((a: A) | (b: B) -> C { /\*...*\/ );</code> | BitOr |
//! | ^ | `overload!((a: A) ^ (b: B) -> C { /*...*/ );` | BitXor |
//! | << | `overload!((a: A) << (b: B) -> C { /*...*/ );` | Shl |
//! | >> | `overload!((a: A) >> (b: B) -> C { /*...*/ );` | Shr |
//!
//! # Assignment operators
//!
//! The general syntax to overload an assignment operator between types `<a_type>` and `<b_type>` is:
//! ```ignore
//! overload!((<a_ident>: &mut <a_type>) <op> (<b_ident>: <b_type>) { /*body*/ });
//! ```
//! Inside the body you can use `<a_ident>` and `<b_ident>` freely to perform any computation and mutate `<a_ident>` as desired.
//!
//! | Operator | Example | Trait |
//! |----------|------------------------------------------------------------------|--------------|
//! | += | `overload!((a: &mut A) += (b: B) { /*...*/ );` | AddAssign |
//! | -= | `overload!((a: &mut A) -= (b: B) { /*...*/ );` | SubAssign |
//! | *= | `overload!((a: &mut A) *= (b: B) { /*...*/ );` | MulAssign |
//! | /= | `overload!((a: &mut A) /= (b: B) { /*...*/ );` | DivAssign |
//! | %= | `overload!((a: &mut A) %= (b: B) { /*...*/ );` | RemAssign |
//! | &= | `overload!((a: &mut A) &= (b: B) { /*...*/ );` | BitAndAssign |
//! | \|= | <code>overload!((a: &mut A) |= (b: B) { /\*...*\/ );</code> | BitOrAssign |
//! | ^= | `overload!((a: &mut A) ^= (b: B) { /*...*/ );` | BitXorAssign |
//! | <<= | `overload!((a: &mut A) <<= (b: B) { /*...*/ );` | ShlAssign |
//! | >>= | `overload!((a: &mut A) >>= (b: B) { /*...*/ );` | ShrAssign |
//!
//! # Unary operators
//!
//! The general syntax to overload a unary operator for type `<a_type>` is:
//! ```ignore
//! overload!(<op> (<a_ident>: <a_type>) -> <out_type> { /*body*/ });
//! ```
//! Inside the body you can use `<a_ident>` freely to perform any computation.
//!
//! The last line of the body needs to be an expression (i.e. no `;` at the end of the line) of type `<out_type>`.
//!
//! | Operator | Example | Trait |
//! |----------|---------------------------------------------------------|-------|
//! | - | `overload!(- (a: A) -> B { /*...*/ );` | Neg |
//! | ! | `overload!(! (a: A) -> B { /*...*/ );` | Not |
//!
//! # Notes
//!
//! Remember that you can only overload operators between one or more types if at least one of the types is defined in the current crate.
/// Overloads an operator. See the [module level documentation](index.html) for more information.