rust/src/libcore/ops.rs

// Copyright 2012 The Rust Project Developers. See the COPYRIGHT
// file at the top-level directory of this distribution and at
// http://rust-lang.org/COPYRIGHT.
//
// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
// option. This file may not be copied, modified, or distributed
// except according to those terms.

/*!
 *
 * Overloadable operators
 *
 * Implementing these traits allows you to get an effect similar to
 * overloading operators.
 *
 * The values for the right hand side of an operator are automatically
 * borrowed, so `a + b` is sugar for `a.add(&b)`.
 *
 * All of these traits are imported by the prelude, so they are available in
 * every Rust program.
 *
 * # Example
 *
 * This example creates a `Point` struct that implements `Add` and `Sub`, and then
 * demonstrates adding and subtracting two `Point`s.
 *
 * ```rust
 * #[deriving(Show)]
 * struct Point {
 *     x: int,
 *     y: int
 * }
 *
 * impl Add<Point, Point> for Point {
 *     fn add(&self, other: &Point) -> Point {
 *         Point {x: self.x + other.x, y: self.y + other.y}
 *     }
 * }
 *
 * impl Sub<Point, Point> for Point {
 *     fn sub(&self, other: &Point) -> Point {
 *         Point {x: self.x - other.x, y: self.y - other.y}
 *     }
 * }
 * fn main() {
 *     println!("{}", Point {x: 1, y: 0} + Point {x: 2, y: 3});
 *     println!("{}", Point {x: 1, y: 0} - Point {x: 2, y: 3});
 * }
 * ```
 *
 * See the documentation for each trait for a minimum implementation that prints
 * something to the screen.
 *
 */

use kinds::Sized;

/**
 *
 * The `Drop` trait is used to run some code when a value goes out of scope. This
 * is sometimes called a 'destructor'.
 *
 * # Example
 *
 * A trivial implementation of `Drop`. The `drop` method is called when `_x` goes
 * out of scope, and therefore `main` prints `Dropping!`.
 *
 * ```rust
 * struct HasDrop;
 *
 * impl Drop for HasDrop {
 *   fn drop(&mut self) {
 *       println!("Dropping!");
 *   }
 * }
 *
 * fn main() {
 *   let _x = HasDrop;
 * }
 * ```
 */
#[lang="drop"]
pub trait Drop {
    /// The `drop` method, called when the value goes out of scope.
    fn drop(&mut self);
}

/**
 *
 * The `Add` trait is used to specify the functionality of `+`.
 *
 * # Example
 *
 * A trivial implementation of `Add`. When `Foo + Foo` happens, it ends up
 * calling `add`, and therefore, `main` prints `Adding!`.
 *
 * ```rust
 * struct Foo;
 *
 * impl Add<Foo, Foo> for Foo {
 *     fn add(&self, _rhs: &Foo) -> Foo {
 *       println!("Adding!");
 *       *self
 *   }
 * }
 *
 * fn main() {
 *   Foo + Foo;
 * }
 * ```
 */
#[lang="add"]
pub trait Add<Sized? RHS,Result> for Sized? {
    /// The method for the `+` operator
    fn add(&self, rhs: &RHS) -> Result;
}

macro_rules! add_impl(
    ($($t:ty)*) => ($(
        impl Add<$t, $t> for $t {
            #[inline]
            fn add(&self, other: &$t) -> $t { (*self) + (*other) }
        }
    )*)
)

add_impl!(uint u8 u16 u32 u64 int i8 i16 i32 i64 f32 f64)

/**
 *
 * The `Sub` trait is used to specify the functionality of `-`.
 *
 * # Example
 *
 * A trivial implementation of `Sub`. When `Foo - Foo` happens, it ends up
 * calling `sub`, and therefore, `main` prints `Subtracting!`.
 *
 * ```rust
 * struct Foo;
 *
 * impl Sub<Foo, Foo> for Foo {
 *     fn sub(&self, _rhs: &Foo) -> Foo {
 *         println!("Subtracting!");
 *         *self
 *     }
 * }
 *
 * fn main() {
 *     Foo - Foo;
 * }
 * ```
 */
#[lang="sub"]
pub trait Sub<Sized? RHS, Result> for Sized? {
    /// The method for the `-` operator
    fn sub(&self, rhs: &RHS) -> Result;
}

macro_rules! sub_impl(
    ($($t:ty)*) => ($(
        impl Sub<$t, $t> for $t {
            #[inline]
            fn sub(&self, other: &$t) -> $t { (*self) - (*other) }
        }
    )*)
)

sub_impl!(uint u8 u16 u32 u64 int i8 i16 i32 i64 f32 f64)

/**
 *
 * The `Mul` trait is used to specify the functionality of `*`.
 *
 * # Example
 *
 * A trivial implementation of `Mul`. When `Foo * Foo` happens, it ends up
 * calling `mul`, and therefore, `main` prints `Multiplying!`.
 *
 * ```rust
 * struct Foo;
 *
 * impl Mul<Foo, Foo> for Foo {
 *     fn mul(&self, _rhs: &Foo) -> Foo {
 *         println!("Multiplying!");
 *         *self
 *     }
 * }
 *
 * fn main() {
 *     Foo * Foo;
 * }
 * ```
 */
#[lang="mul"]
pub trait Mul<Sized? RHS, Result>  for Sized? {
    /// The method for the `*` operator
    fn mul(&self, rhs: &RHS) -> Result;
}

macro_rules! mul_impl(
    ($($t:ty)*) => ($(
        impl Mul<$t, $t> for $t {
            #[inline]
            fn mul(&self, other: &$t) -> $t { (*self) * (*other) }
        }
    )*)
)

mul_impl!(uint u8 u16 u32 u64 int i8 i16 i32 i64 f32 f64)

/**
 *
 * The `Div` trait is used to specify the functionality of `/`.
 *
 * # Example
 *
 * A trivial implementation of `Div`. When `Foo / Foo` happens, it ends up
 * calling `div`, and therefore, `main` prints `Dividing!`.
 *
 * ```
 * struct Foo;
 *
 * impl Div<Foo, Foo> for Foo {
 *     fn div(&self, _rhs: &Foo) -> Foo {
 *         println!("Dividing!");
 *         *self
 *     }
 * }
 *
 * fn main() {
 *     Foo / Foo;
 * }
 * ```
 */
#[lang="div"]
pub trait Div<Sized? RHS, Result> for Sized? {
    /// The method for the `/` operator
    fn div(&self, rhs: &RHS) -> Result;
}

macro_rules! div_impl(
    ($($t:ty)*) => ($(
        impl Div<$t, $t> for $t {
            #[inline]
            fn div(&self, other: &$t) -> $t { (*self) / (*other) }
        }
    )*)
)

div_impl!(uint u8 u16 u32 u64 int i8 i16 i32 i64 f32 f64)

/**
 *
 * The `Rem` trait is used to specify the functionality of `%`.
 *
 * # Example
 *
 * A trivial implementation of `Rem`. When `Foo % Foo` happens, it ends up
 * calling `rem`, and therefore, `main` prints `Remainder-ing!`.
 *
 * ```
 * struct Foo;
 *
 * impl Rem<Foo, Foo> for Foo {
 *     fn rem(&self, _rhs: &Foo) -> Foo {
 *         println!("Remainder-ing!");
 *         *self
 *     }
 * }
 *
 * fn main() {
 *     Foo % Foo;
 * }
 * ```
 */
#[lang="rem"]
pub trait Rem<Sized? RHS, Result>  for Sized? {
    /// The method for the `%` operator
    fn rem(&self, rhs: &RHS) -> Result;
}

macro_rules! rem_impl(
    ($($t:ty)*) => ($(
        impl Rem<$t, $t> for $t {
            #[inline]
            fn rem(&self, other: &$t) -> $t { (*self) % (*other) }
        }
    )*)
)

macro_rules! rem_float_impl(
    ($t:ty, $fmod:ident) => {
        impl Rem<$t, $t> for $t {
            #[inline]
            fn rem(&self, other: &$t) -> $t {
                extern { fn $fmod(a: $t, b: $t) -> $t; }
                unsafe { $fmod(*self, *other) }
            }
        }
    }
)

rem_impl!(uint u8 u16 u32 u64 int i8 i16 i32 i64)
rem_float_impl!(f32, fmodf)
rem_float_impl!(f64, fmod)

/**
 *
 * The `Neg` trait is used to specify the functionality of unary `-`.
 *
 * # Example
 *
 * A trivial implementation of `Neg`. When `-Foo` happens, it ends up calling
 * `neg`, and therefore, `main` prints `Negating!`.
 *
 * ```
 * struct Foo;
 *
 * impl Neg<Foo> for Foo {
 *     fn neg(&self) -> Foo {
 *         println!("Negating!");
 *         *self
 *     }
 * }
 *
 * fn main() {
 *     -Foo;
 * }
 * ```
 */
#[lang="neg"]
pub trait Neg<Result> for Sized? {
    /// The method for the unary `-` operator
    fn neg(&self) -> Result;
}

macro_rules! neg_impl(
    ($($t:ty)*) => ($(
        impl Neg<$t> for $t {
            #[inline]
            fn neg(&self) -> $t { -*self }
        }
    )*)
)

macro_rules! neg_uint_impl(
    ($t:ty, $t_signed:ty) => {
        impl Neg<$t> for $t {
            #[inline]
            fn neg(&self) -> $t { -(*self as $t_signed) as $t }
        }
    }
)

neg_impl!(int i8 i16 i32 i64 f32 f64)

neg_uint_impl!(uint, int)
neg_uint_impl!(u8, i8)
neg_uint_impl!(u16, i16)
neg_uint_impl!(u32, i32)
neg_uint_impl!(u64, i64)


/**
 *
 * The `Not` trait is used to specify the functionality of unary `!`.
 *
 * # Example
 *
 * A trivial implementation of `Not`. When `!Foo` happens, it ends up calling
 * `not`, and therefore, `main` prints `Not-ing!`.
 *
 * ```
 * struct Foo;
 *
 * impl Not<Foo> for Foo {
 *     fn not(&self) -> Foo {
 *         println!("Not-ing!");
 *         *self
 *     }
 * }
 *
 * fn main() {
 *     !Foo;
 * }
 * ```
 */
#[lang="not"]
pub trait Not<Result> for Sized? {
    /// The method for the unary `!` operator
    fn not(&self) -> Result;
}


macro_rules! not_impl(
    ($($t:ty)*) => ($(
        impl Not<$t> for $t {
            #[inline]
            fn not(&self) -> $t { !*self }
        }
    )*)
)

not_impl!(bool uint u8 u16 u32 u64 int i8 i16 i32 i64)

/**
 *
 * The `BitAnd` trait is used to specify the functionality of `&`.
 *
 * # Example
 *
 * A trivial implementation of `BitAnd`. When `Foo & Foo` happens, it ends up
 * calling `bitand`, and therefore, `main` prints `Bitwise And-ing!`.
 *
 * ```
 * struct Foo;
 *
 * impl BitAnd<Foo, Foo> for Foo {
 *     fn bitand(&self, _rhs: &Foo) -> Foo {
 *         println!("Bitwise And-ing!");
 *         *self
 *     }
 * }
 *
 * fn main() {
 *     Foo & Foo;
 * }
 * ```
 */
#[lang="bitand"]
pub trait BitAnd<Sized? RHS, Result> for Sized? {
    /// The method for the `&` operator
    fn bitand(&self, rhs: &RHS) -> Result;
}

macro_rules! bitand_impl(
    ($($t:ty)*) => ($(
        impl BitAnd<$t, $t> for $t {
            #[inline]
            fn bitand(&self, rhs: &$t) -> $t { (*self) & (*rhs) }
        }
    )*)
)

bitand_impl!(bool uint u8 u16 u32 u64 int i8 i16 i32 i64)

/**
 *
 * The `BitOr` trait is used to specify the functionality of `|`.
 *
 * # Example
 *
 * A trivial implementation of `BitOr`. When `Foo | Foo` happens, it ends up
 * calling `bitor`, and therefore, `main` prints `Bitwise Or-ing!`.
 *
 * ```
 * struct Foo;
 *
 * impl BitOr<Foo, Foo> for Foo {
 *     fn bitor(&self, _rhs: &Foo) -> Foo {
 *         println!("Bitwise Or-ing!");
 *         *self
 *     }
 * }
 *
 * fn main() {
 *     Foo | Foo;
 * }
 * ```
 */
#[lang="bitor"]
pub trait BitOr<Sized? RHS, Result> for Sized? {
    /// The method for the `|` operator
    fn bitor(&self, rhs: &RHS) -> Result;
}

macro_rules! bitor_impl(
    ($($t:ty)*) => ($(
        impl BitOr<$t,$t> for $t {
            #[inline]
            fn bitor(&self, rhs: &$t) -> $t { (*self) | (*rhs) }
        }
    )*)
)

bitor_impl!(bool uint u8 u16 u32 u64 int i8 i16 i32 i64)

/**
 *
 * The `BitXor` trait is used to specify the functionality of `^`.
 *
 * # Example
 *
 * A trivial implementation of `BitXor`. When `Foo ^ Foo` happens, it ends up
 * calling `bitxor`, and therefore, `main` prints `Bitwise Xor-ing!`.
 *
 * ```
 * struct Foo;
 *
 * impl BitXor<Foo, Foo> for Foo {
 *     fn bitxor(&self, _rhs: &Foo) -> Foo {
 *         println!("Bitwise Xor-ing!");
 *         *self
 *     }
 * }
 *
 * fn main() {
 *     Foo ^ Foo;
 * }
 * ```
 */
#[lang="bitxor"]
pub trait BitXor<Sized? RHS, Result> for Sized? {
    /// The method for the `^` operator
    fn bitxor(&self, rhs: &RHS) -> Result;
}

macro_rules! bitxor_impl(
    ($($t:ty)*) => ($(
        impl BitXor<$t, $t> for $t {
            #[inline]
            fn bitxor(&self, other: &$t) -> $t { (*self) ^ (*other) }
        }
    )*)
)

bitxor_impl!(bool uint u8 u16 u32 u64 int i8 i16 i32 i64)

/**
 *
 * The `Shl` trait is used to specify the functionality of `<<`.
 *
 * # Example
 *
 * A trivial implementation of `Shl`. When `Foo << Foo` happens, it ends up
 * calling `shl`, and therefore, `main` prints `Shifting left!`.
 *
 * ```
 * struct Foo;
 *
 * impl Shl<Foo, Foo> for Foo {
 *     fn shl(&self, _rhs: &Foo) -> Foo {
 *         println!("Shifting left!");
 *         *self
 *     }
 * }
 *
 * fn main() {
 *     Foo << Foo;
 * }
 * ```
 */
#[lang="shl"]
pub trait Shl<Sized? RHS, Result> for Sized? {
    /// The method for the `<<` operator
    fn shl(&self, rhs: &RHS) -> Result;
}

macro_rules! shl_impl(
    ($($t:ty)*) => ($(
        impl Shl<uint, $t> for $t {
            #[inline]
            fn shl(&self, other: &uint) -> $t {
                (*self) << (*other)
            }
        }
    )*)
)

shl_impl!(uint u8 u16 u32 u64 int i8 i16 i32 i64)

/**
 *
 * The `Shr` trait is used to specify the functionality of `>>`.
 *
 * # Example
 *
 * A trivial implementation of `Shr`. When `Foo >> Foo` happens, it ends up
 * calling `shr`, and therefore, `main` prints `Shifting right!`.
 *
 * ```
 * struct Foo;
 *
 * impl Shr<Foo, Foo> for Foo {
 *     fn shr(&self, _rhs: &Foo) -> Foo {
 *         println!("Shifting right!");
 *         *self
 *     }
 * }
 *
 * fn main() {
 *     Foo >> Foo;
 * }
 * ```
 */
#[lang="shr"]
pub trait Shr<Sized? RHS, Result> for Sized? {
    /// The method for the `>>` operator
    fn shr(&self, rhs: &RHS) -> Result;
}

macro_rules! shr_impl(
    ($($t:ty)*) => ($(
        impl Shr<uint, $t> for $t {
            #[inline]
            fn shr(&self, other: &uint) -> $t { (*self) >> (*other) }
        }
    )*)
)

shr_impl!(uint u8 u16 u32 u64 int i8 i16 i32 i64)

/**
 *
 * The `Index` trait is used to specify the functionality of indexing operations
 * like `arr[idx]` when used in an immutable context.
 *
 * # Example
 *
 * A trivial implementation of `Index`. When `Foo[Foo]` happens, it ends up
 * calling `index`, and therefore, `main` prints `Indexing!`.
 *
 * ```
 * struct Foo;
 *
 * impl Index<Foo, Foo> for Foo {
 *     fn index<'a>(&'a self, _index: &Foo) -> &'a Foo {
 *         println!("Indexing!");
 *         self
 *     }
 * }
 *
 * fn main() {
 *     Foo[Foo];
 * }
 * ```
 */
#[lang="index"]
pub trait Index<Sized? Index, Sized? Result> for Sized? {
    /// The method for the indexing (`Foo[Bar]`) operation
    fn index<'a>(&'a self, index: &Index) -> &'a Result;
}

/**
 *
 * The `IndexMut` trait is used to specify the functionality of indexing
 * operations like `arr[idx]`, when used in a mutable context.
 *
 * # Example
 *
 * A trivial implementation of `IndexMut`. When `Foo[Foo]` happens, it ends up
 * calling `index_mut`, and therefore, `main` prints `Indexing!`.
 *
 * ```
 * struct Foo;
 *
 * impl IndexMut<Foo, Foo> for Foo {
 *     fn index_mut<'a>(&'a mut self, _index: &Foo) -> &'a mut Foo {
 *         println!("Indexing!");
 *         self
 *     }
 * }
 *
 * fn main() {
 *     &mut Foo[Foo];
 * }
 * ```
 */
#[lang="index_mut"]
pub trait IndexMut<Sized? Index, Sized? Result> for Sized? {
    /// The method for the indexing (`Foo[Bar]`) operation
    fn index_mut<'a>(&'a mut self, index: &Index) -> &'a mut Result;
}

/**
 *
 * The `Slice` trait is used to specify the functionality of slicing operations
 * like `arr[from..to]` when used in an immutable context.
 *
 * # Example
 *
 * A trivial implementation of `Slice`. When `Foo[..Foo]` happens, it ends up
 * calling `slice_to`, and therefore, `main` prints `Slicing!`.
 *
 * ```ignore
 * struct Foo;
 *
 * impl Slice<Foo, Foo> for Foo {
 *     fn as_slice_<'a>(&'a self) -> &'a Foo {
 *         println!("Slicing!");
 *         self
 *     }
 *     fn slice_from_or_fail<'a>(&'a self, _from: &Foo) -> &'a Foo {
 *         println!("Slicing!");
 *         self
 *     }
 *     fn slice_to_or_fail<'a>(&'a self, _to: &Foo) -> &'a Foo {
 *         println!("Slicing!");
 *         self
 *     }
 *     fn slice_or_fail<'a>(&'a self, _from: &Foo, _to: &Foo) -> &'a Foo {
 *         println!("Slicing!");
 *         self
 *     }
 * }
 *
 * fn main() {
 *     Foo[..Foo];
 * }
 * ```
 */
#[lang="slice"]
pub trait Slice<Sized? Idx, Sized? Result> for Sized? {
    /// The method for the slicing operation foo[]
    fn as_slice_<'a>(&'a self) -> &'a Result;
    /// The method for the slicing operation foo[from..]
    fn slice_from_or_fail<'a>(&'a self, from: &Idx) -> &'a Result;
    /// The method for the slicing operation foo[..to]
    fn slice_to_or_fail<'a>(&'a self, to: &Idx) -> &'a Result;
    /// The method for the slicing operation foo[from..to]
    fn slice_or_fail<'a>(&'a self, from: &Idx, to: &Idx) -> &'a Result;
}

/**
 *
 * The `SliceMut` trait is used to specify the functionality of slicing
 * operations like `arr[from..to]`, when used in a mutable context.
 *
 * # Example
 *
 * A trivial implementation of `SliceMut`. When `Foo[Foo..]` happens, it ends up
 * calling `slice_from_mut`, and therefore, `main` prints `Slicing!`.
 *
 * ```ignore
 * struct Foo;
 *
 * impl SliceMut<Foo, Foo> for Foo {
 *     fn as_mut_slice_<'a>(&'a mut self) -> &'a mut Foo {
 *         println!("Slicing!");
 *         self
 *     }
 *     fn slice_from_or_fail_mut<'a>(&'a mut self, _from: &Foo) -> &'a mut Foo {
 *         println!("Slicing!");
 *         self
 *     }
 *     fn slice_to_or_fail_mut<'a>(&'a mut self, _to: &Foo) -> &'a mut Foo {
 *         println!("Slicing!");
 *         self
 *     }
 *     fn slice_or_fail_mut<'a>(&'a mut self, _from: &Foo, _to: &Foo) -> &'a mut Foo {
 *         println!("Slicing!");
 *         self
 *     }
 * }
 *
 * pub fn main() {
 *     Foo[mut Foo..];
 * }
 * ```
 */
#[lang="slice_mut"]
pub trait SliceMut<Sized? Idx, Sized? Result> for Sized? {
    /// The method for the slicing operation foo[]
    fn as_mut_slice_<'a>(&'a mut self) -> &'a mut Result;
    /// The method for the slicing operation foo[from..]
    fn slice_from_or_fail_mut<'a>(&'a mut self, from: &Idx) -> &'a mut Result;
    /// The method for the slicing operation foo[..to]
    fn slice_to_or_fail_mut<'a>(&'a mut self, to: &Idx) -> &'a mut Result;
    /// The method for the slicing operation foo[from..to]
    fn slice_or_fail_mut<'a>(&'a mut self, from: &Idx, to: &Idx) -> &'a mut Result;
}

/**
 *
 * The `Deref` trait is used to specify the functionality of dereferencing
 * operations like `*v`.
 *
 * # Example
 *
 * A struct with a single field which is accessible via dereferencing the
 * struct.
 *
 * ```
 * struct DerefExample<T> {
 *     value: T
 * }
 *
 * impl<T> Deref<T> for DerefExample<T> {
 *     fn deref<'a>(&'a self) -> &'a T {
 *         &self.value
 *     }
 * }
 *
 * fn main() {
 *     let x = DerefExample { value: 'a' };
 *     assert_eq!('a', *x);
 * }
 * ```
 */
#[lang="deref"]
pub trait Deref<Sized? Result> for Sized? {
    /// The method called to dereference a value
    fn deref<'a>(&'a self) -> &'a Result;
}

impl<'a, Sized? T> Deref<T> for &'a T {
    fn deref(&self) -> &T { *self }
}

impl<'a, Sized? T> Deref<T> for &'a mut T {
    fn deref(&self) -> &T { *self }
}

/**
 *
 * The `DerefMut` trait is used to specify the functionality of dereferencing
 * mutably like `*v = 1;`
 *
 * # Example
 *
 * A struct with a single field which is modifiable via dereferencing the
 * struct.
 *
 * ```
 * struct DerefMutExample<T> {
 *     value: T
 * }
 *
 * impl<T> Deref<T> for DerefMutExample<T> {
 *     fn deref<'a>(&'a self) -> &'a T {
 *         &self.value
 *     }
 * }
 *
 * impl<T> DerefMut<T> for DerefMutExample<T> {
 *     fn deref_mut<'a>(&'a mut self) -> &'a mut T {
 *         &mut self.value
 *     }
 * }
 *
 * fn main() {
 *     let mut x = DerefMutExample { value: 'a' };
 *     *x = 'b';
 *     assert_eq!('b', *x);
 * }
 * ```
 */
#[lang="deref_mut"]
pub trait DerefMut<Sized? Result>: Deref<Result> {
    /// The method called to mutably dereference a value
    fn deref_mut<'a>(&'a mut self) -> &'a mut Result;
}

impl<'a, Sized? T> DerefMut<T> for &'a mut T {
    fn deref_mut(&mut self) -> &mut T { *self }
}

/// A version of the call operator that takes an immutable receiver.
#[lang="fn"]
pub trait Fn<Args,Result> for Sized? {
    /// This is called when the call operator is used.
    extern "rust-call" fn call(&self, args: Args) -> Result;
}

/// A version of the call operator that takes a mutable receiver.
#[lang="fn_mut"]
pub trait FnMut<Args,Result> for Sized? {
    /// This is called when the call operator is used.
    extern "rust-call" fn call_mut(&mut self, args: Args) -> Result;
}

/// A version of the call operator that takes a by-value receiver.
#[lang="fn_once"]
pub trait FnOnce<Args,Result> for Sized? {
    /// This is called when the call operator is used.
    extern "rust-call" fn call_once(self, args: Args) -> Result;
}

impl<F,A,R> FnMut<A,R> for F
    where F : Fn<A,R>
{
    extern "rust-call" fn call_mut(&mut self, args: A) -> R {
        self.call(args)
    }
}

impl<F,A,R> FnOnce<A,R> for F
    where F : FnMut<A,R>
{
    extern "rust-call" fn call_once(mut self, args: A) -> R {
        self.call_mut(args)
    }
}


impl<Result> Fn<(),Result> for extern "Rust" fn() -> Result {
    #[allow(non_snake_case)]
    extern "rust-call" fn call(&self, _args: ()) -> Result {
        (*self)()
    }
}

impl<Result,A0> Fn<(A0,),Result> for extern "Rust" fn(A0) -> Result {
    #[allow(non_snake_case)]
    extern "rust-call" fn call(&self, args: (A0,)) -> Result {
        let (a0,) = args;
        (*self)(a0)
    }
}

macro_rules! def_fn(
    ($($args:ident)*) => (
        impl<Result$(,$args)*>
        Fn<($($args,)*),Result>
        for extern "Rust" fn($($args: $args,)*) -> Result {
            #[allow(non_snake_case)]
            extern "rust-call" fn call(&self, args: ($($args,)*)) -> Result {
                let ($($args,)*) = args;
                (*self)($($args,)*)
            }
        }
    )
)

def_fn!(A0 A1)
def_fn!(A0 A1 A2)
def_fn!(A0 A1 A2 A3)
def_fn!(A0 A1 A2 A3 A4)
def_fn!(A0 A1 A2 A3 A4 A5)
def_fn!(A0 A1 A2 A3 A4 A5 A6)
def_fn!(A0 A1 A2 A3 A4 A5 A6 A7)
def_fn!(A0 A1 A2 A3 A4 A5 A6 A7 A8)
def_fn!(A0 A1 A2 A3 A4 A5 A6 A7 A8 A9)
def_fn!(A0 A1 A2 A3 A4 A5 A6 A7 A8 A9 A10)
def_fn!(A0 A1 A2 A3 A4 A5 A6 A7 A8 A9 A10 A11)
def_fn!(A0 A1 A2 A3 A4 A5 A6 A7 A8 A9 A10 A11 A12)
def_fn!(A0 A1 A2 A3 A4 A5 A6 A7 A8 A9 A10 A11 A12 A13)
def_fn!(A0 A1 A2 A3 A4 A5 A6 A7 A8 A9 A10 A11 A12 A13 A14)
def_fn!(A0 A1 A2 A3 A4 A5 A6 A7 A8 A9 A10 A11 A12 A13 A14 A15)