rust/src/libcore/ops.rs
2015-01-06 21:26:48 -08:00

1083 lines
23 KiB
Rust

// 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
//! #![feature(associated_types)]
//!
//! use std::ops::{Add, Sub};
//!
//! #[derive(Show)]
//! struct Point {
//! x: int,
//! y: int
//! }
//!
//! impl Add for Point {
//! type Output = Point;
//!
//! fn add(self, other: Point) -> Point {
//! Point {x: self.x + other.x, y: self.y + other.y}
//! }
//! }
//!
//! impl Sub for Point {
//! type Output = 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.
#![stable]
use clone::Clone;
use iter::{Step, Iterator,DoubleEndedIterator,ExactSizeIterator};
use marker::Sized;
use option::Option::{self, Some, None};
/// 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"]
#[stable]
pub trait Drop {
/// The `drop` method, called when the value goes out of scope.
#[stable]
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
/// #![feature(associated_types)]
///
/// use std::ops::Add;
///
/// #[derive(Copy)]
/// struct Foo;
///
/// impl Add for Foo {
/// type Output = Foo;
///
/// fn add(self, _rhs: Foo) -> Foo {
/// println!("Adding!");
/// self
/// }
/// }
///
/// fn main() {
/// Foo + Foo;
/// }
/// ```
#[lang="add"]
#[stable]
pub trait Add<RHS=Self> {
#[stable]
type Output;
/// The method for the `+` operator
#[stable]
fn add(self, rhs: RHS) -> Self::Output;
}
macro_rules! add_impl {
($($t:ty)*) => ($(
#[stable]
impl Add for $t {
type Output = $t;
#[inline]
fn add(self, other: $t) -> $t { self + other }
}
)*)
}
add_impl! { uint u8 u16 u32 u64 int i8 i16 i32 i64 f32 f64 }
/// The `Sub` trait is used to specify the functionality of `-`.
///
/// # Example
///
/// A trivial implementation of `Sub`. When `Foo - Foo` happens, it ends up
/// calling `sub`, and therefore, `main` prints `Subtracting!`.
///
/// ```rust
/// #![feature(associated_types)]
///
/// use std::ops::Sub;
///
/// #[derive(Copy)]
/// struct Foo;
///
/// impl Sub for Foo {
/// type Output = Foo;
///
/// fn sub(self, _rhs: Foo) -> Foo {
/// println!("Subtracting!");
/// self
/// }
/// }
///
/// fn main() {
/// Foo - Foo;
/// }
/// ```
#[lang="sub"]
#[stable]
pub trait Sub<RHS=Self> {
#[stable]
type Output;
/// The method for the `-` operator
#[stable]
fn sub(self, rhs: RHS) -> Self::Output;
}
macro_rules! sub_impl {
($($t:ty)*) => ($(
#[stable]
impl Sub for $t {
type Output = $t;
#[inline]
fn sub(self, other: $t) -> $t { self - other }
}
)*)
}
sub_impl! { uint u8 u16 u32 u64 int i8 i16 i32 i64 f32 f64 }
/// The `Mul` trait is used to specify the functionality of `*`.
///
/// # Example
///
/// A trivial implementation of `Mul`. When `Foo * Foo` happens, it ends up
/// calling `mul`, and therefore, `main` prints `Multiplying!`.
///
/// ```rust
/// #![feature(associated_types)]
///
/// use std::ops::Mul;
///
/// #[derive(Copy)]
/// struct Foo;
///
/// impl Mul for Foo {
/// type Output = Foo;
///
/// fn mul(self, _rhs: Foo) -> Foo {
/// println!("Multiplying!");
/// self
/// }
/// }
///
/// fn main() {
/// Foo * Foo;
/// }
/// ```
#[lang="mul"]
#[stable]
pub trait Mul<RHS=Self> {
#[stable]
type Output;
/// The method for the `*` operator
#[stable]
fn mul(self, rhs: RHS) -> Self::Output;
}
macro_rules! mul_impl {
($($t:ty)*) => ($(
#[stable]
impl Mul for $t {
type Output = $t;
#[inline]
fn mul(self, other: $t) -> $t { self * other }
}
)*)
}
mul_impl! { uint u8 u16 u32 u64 int i8 i16 i32 i64 f32 f64 }
/// The `Div` trait is used to specify the functionality of `/`.
///
/// # Example
///
/// A trivial implementation of `Div`. When `Foo / Foo` happens, it ends up
/// calling `div`, and therefore, `main` prints `Dividing!`.
///
/// ```
/// #![feature(associated_types)]
///
/// use std::ops::Div;
///
/// #[derive(Copy)]
/// struct Foo;
///
/// impl Div for Foo {
/// type Output = Foo;
///
/// fn div(self, _rhs: Foo) -> Foo {
/// println!("Dividing!");
/// self
/// }
/// }
///
/// fn main() {
/// Foo / Foo;
/// }
/// ```
#[lang="div"]
#[stable]
pub trait Div<RHS=Self> {
#[stable]
type Output;
/// The method for the `/` operator
#[stable]
fn div(self, rhs: RHS) -> Self::Output;
}
macro_rules! div_impl {
($($t:ty)*) => ($(
#[stable]
impl Div for $t {
type Output = $t;
#[inline]
fn div(self, other: $t) -> $t { self / other }
}
)*)
}
div_impl! { uint u8 u16 u32 u64 int i8 i16 i32 i64 f32 f64 }
/// The `Rem` trait is used to specify the functionality of `%`.
///
/// # Example
///
/// A trivial implementation of `Rem`. When `Foo % Foo` happens, it ends up
/// calling `rem`, and therefore, `main` prints `Remainder-ing!`.
///
/// ```
/// #![feature(associated_types)]
///
/// use std::ops::Rem;
///
/// #[derive(Copy)]
/// struct Foo;
///
/// impl Rem for Foo {
/// type Output = Foo;
///
/// fn rem(self, _rhs: Foo) -> Foo {
/// println!("Remainder-ing!");
/// self
/// }
/// }
///
/// fn main() {
/// Foo % Foo;
/// }
/// ```
#[lang="rem"]
#[stable]
pub trait Rem<RHS=Self> {
#[stable]
type Output = Self;
/// The method for the `%` operator
#[stable]
fn rem(self, rhs: RHS) -> Self::Output;
}
macro_rules! rem_impl {
($($t:ty)*) => ($(
#[stable]
impl Rem for $t {
type Output = $t;
#[inline]
fn rem(self, other: $t) -> $t { self % other }
}
)*)
}
macro_rules! rem_float_impl {
($t:ty, $fmod:ident) => {
#[stable]
impl Rem for $t {
type Output = $t;
#[inline]
fn rem(self, other: $t) -> $t {
extern { fn $fmod(a: $t, b: $t) -> $t; }
unsafe { $fmod(self, other) }
}
}
}
}
rem_impl! { uint u8 u16 u32 u64 int i8 i16 i32 i64 }
rem_float_impl! { f32, fmodf }
rem_float_impl! { f64, fmod }
/// The `Neg` trait is used to specify the functionality of unary `-`.
///
/// # Example
///
/// A trivial implementation of `Neg`. When `-Foo` happens, it ends up calling
/// `neg`, and therefore, `main` prints `Negating!`.
///
/// ```
/// #![feature(associated_types)]
///
/// use std::ops::Neg;
///
/// struct Foo;
///
/// impl Copy for Foo {}
///
/// impl Neg for Foo {
/// type Output = Foo;
///
/// fn neg(self) -> Foo {
/// println!("Negating!");
/// self
/// }
/// }
///
/// fn main() {
/// -Foo;
/// }
/// ```
#[lang="neg"]
#[stable]
pub trait Neg {
#[stable]
type Output;
/// The method for the unary `-` operator
#[stable]
fn neg(self) -> Self::Output;
}
macro_rules! neg_impl {
($($t:ty)*) => ($(
#[stable]
impl Neg for $t {
#[stable]
type Output = $t;
#[inline]
#[stable]
fn neg(self) -> $t { -self }
}
)*)
}
macro_rules! neg_uint_impl {
($t:ty, $t_signed:ty) => {
#[stable]
impl Neg for $t {
type Output = $t;
#[inline]
fn neg(self) -> $t { -(self as $t_signed) as $t }
}
}
}
neg_impl! { int i8 i16 i32 i64 f32 f64 }
neg_uint_impl! { uint, int }
neg_uint_impl! { u8, i8 }
neg_uint_impl! { u16, i16 }
neg_uint_impl! { u32, i32 }
neg_uint_impl! { u64, i64 }
/// The `Not` trait is used to specify the functionality of unary `!`.
///
/// # Example
///
/// A trivial implementation of `Not`. When `!Foo` happens, it ends up calling
/// `not`, and therefore, `main` prints `Not-ing!`.
///
/// ```
/// #![feature(associated_types)]
///
/// use std::ops::Not;
///
/// struct Foo;
///
/// impl Copy for Foo {}
///
/// impl Not for Foo {
/// type Output = Foo;
///
/// fn not(self) -> Foo {
/// println!("Not-ing!");
/// self
/// }
/// }
///
/// fn main() {
/// !Foo;
/// }
/// ```
#[lang="not"]
#[stable]
pub trait Not {
#[stable]
type Output;
/// The method for the unary `!` operator
#[stable]
fn not(self) -> Self::Output;
}
macro_rules! not_impl {
($($t:ty)*) => ($(
#[stable]
impl Not for $t {
type Output = $t;
#[inline]
fn not(self) -> $t { !self }
}
)*)
}
not_impl! { bool uint u8 u16 u32 u64 int i8 i16 i32 i64 }
/// The `BitAnd` trait is used to specify the functionality of `&`.
///
/// # Example
///
/// A trivial implementation of `BitAnd`. When `Foo & Foo` happens, it ends up
/// calling `bitand`, and therefore, `main` prints `Bitwise And-ing!`.
///
/// ```
/// #![feature(associated_types)]
///
/// use std::ops::BitAnd;
///
/// #[derive(Copy)]
/// struct Foo;
///
/// impl BitAnd for Foo {
/// type Output = Foo;
///
/// fn bitand(self, _rhs: Foo) -> Foo {
/// println!("Bitwise And-ing!");
/// self
/// }
/// }
///
/// fn main() {
/// Foo & Foo;
/// }
/// ```
#[lang="bitand"]
#[stable]
pub trait BitAnd<RHS=Self> {
#[stable]
type Output;
/// The method for the `&` operator
#[stable]
fn bitand(self, rhs: RHS) -> Self::Output;
}
macro_rules! bitand_impl {
($($t:ty)*) => ($(
#[stable]
impl BitAnd for $t {
type Output = $t;
#[inline]
fn bitand(self, rhs: $t) -> $t { self & rhs }
}
)*)
}
bitand_impl! { bool uint u8 u16 u32 u64 int i8 i16 i32 i64 }
/// The `BitOr` trait is used to specify the functionality of `|`.
///
/// # Example
///
/// A trivial implementation of `BitOr`. When `Foo | Foo` happens, it ends up
/// calling `bitor`, and therefore, `main` prints `Bitwise Or-ing!`.
///
/// ```
/// #![feature(associated_types)]
///
/// use std::ops::BitOr;
///
/// #[derive(Copy)]
/// struct Foo;
///
/// impl BitOr for Foo {
/// type Output = Foo;
///
/// fn bitor(self, _rhs: Foo) -> Foo {
/// println!("Bitwise Or-ing!");
/// self
/// }
/// }
///
/// fn main() {
/// Foo | Foo;
/// }
/// ```
#[lang="bitor"]
#[stable]
pub trait BitOr<RHS=Self> {
#[stable]
type Output;
/// The method for the `|` operator
#[stable]
fn bitor(self, rhs: RHS) -> Self::Output;
}
macro_rules! bitor_impl {
($($t:ty)*) => ($(
#[stable]
impl BitOr for $t {
type Output = $t;
#[inline]
fn bitor(self, rhs: $t) -> $t { self | rhs }
}
)*)
}
bitor_impl! { bool uint u8 u16 u32 u64 int i8 i16 i32 i64 }
/// The `BitXor` trait is used to specify the functionality of `^`.
///
/// # Example
///
/// A trivial implementation of `BitXor`. When `Foo ^ Foo` happens, it ends up
/// calling `bitxor`, and therefore, `main` prints `Bitwise Xor-ing!`.
///
/// ```
/// #![feature(associated_types)]
///
/// use std::ops::BitXor;
///
/// #[derive(Copy)]
/// struct Foo;
///
/// impl BitXor for Foo {
/// type Output = Foo;
///
/// fn bitxor(self, _rhs: Foo) -> Foo {
/// println!("Bitwise Xor-ing!");
/// self
/// }
/// }
///
/// fn main() {
/// Foo ^ Foo;
/// }
/// ```
#[lang="bitxor"]
#[stable]
pub trait BitXor<RHS=Self> {
#[stable]
type Output;
/// The method for the `^` operator
#[stable]
fn bitxor(self, rhs: RHS) -> Self::Output;
}
macro_rules! bitxor_impl {
($($t:ty)*) => ($(
#[stable]
impl BitXor for $t {
type Output = $t;
#[inline]
fn bitxor(self, other: $t) -> $t { self ^ other }
}
)*)
}
bitxor_impl! { bool uint u8 u16 u32 u64 int i8 i16 i32 i64 }
/// The `Shl` trait is used to specify the functionality of `<<`.
///
/// # Example
///
/// A trivial implementation of `Shl`. When `Foo << Foo` happens, it ends up
/// calling `shl`, and therefore, `main` prints `Shifting left!`.
///
/// ```
/// #![feature(associated_types)]
///
/// use std::ops::Shl;
///
/// #[derive(Copy)]
/// struct Foo;
///
/// impl Shl<Foo> for Foo {
/// type Output = Foo;
///
/// fn shl(self, _rhs: Foo) -> Foo {
/// println!("Shifting left!");
/// self
/// }
/// }
///
/// fn main() {
/// Foo << Foo;
/// }
/// ```
#[lang="shl"]
#[stable]
pub trait Shl<RHS> {
#[stable]
type Output;
/// The method for the `<<` operator
#[stable]
fn shl(self, rhs: RHS) -> Self::Output;
}
macro_rules! shl_impl {
($($t:ty)*) => ($(
#[stable]
impl Shl<uint> for $t {
type Output = $t;
#[inline]
fn shl(self, other: uint) -> $t {
self << other
}
}
)*)
}
shl_impl! { uint u8 u16 u32 u64 int i8 i16 i32 i64 }
/// The `Shr` trait is used to specify the functionality of `>>`.
///
/// # Example
///
/// A trivial implementation of `Shr`. When `Foo >> Foo` happens, it ends up
/// calling `shr`, and therefore, `main` prints `Shifting right!`.
///
/// ```
/// #![feature(associated_types)]
///
/// use std::ops::Shr;
///
/// #[derive(Copy)]
/// struct Foo;
///
/// impl Shr<Foo> for Foo {
/// type Output = Foo;
///
/// fn shr(self, _rhs: Foo) -> Foo {
/// println!("Shifting right!");
/// self
/// }
/// }
///
/// fn main() {
/// Foo >> Foo;
/// }
/// ```
#[lang="shr"]
#[stable]
pub trait Shr<RHS> {
#[stable]
type Output;
/// The method for the `>>` operator
#[stable]
fn shr(self, rhs: RHS) -> Self::Output;
}
macro_rules! shr_impl {
($($t:ty)*) => ($(
impl Shr<uint> for $t {
type Output = $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!`.
///
/// ```
/// #![feature(associated_types)]
///
/// use std::ops::Index;
///
/// #[derive(Copy)]
/// struct Foo;
///
/// impl Index<Foo> for Foo {
/// type Output = Foo;
///
/// fn index<'a>(&'a self, _index: &Foo) -> &'a Foo {
/// println!("Indexing!");
/// self
/// }
/// }
///
/// fn main() {
/// Foo[Foo];
/// }
/// ```
#[lang="index"]
pub trait Index<Index: ?Sized> {
type Output: ?Sized;
/// The method for the indexing (`Foo[Bar]`) operation
fn index<'a>(&'a self, index: &Index) -> &'a Self::Output;
}
/// 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!`.
///
/// ```
/// #![feature(associated_types)]
///
/// use std::ops::IndexMut;
///
/// #[derive(Copy)]
/// struct Foo;
///
/// impl IndexMut<Foo> for Foo {
/// type Output = 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<Index: ?Sized> {
type Output: ?Sized;
/// The method for the indexing (`Foo[Bar]`) operation
fn index_mut<'a>(&'a mut self, index: &Index) -> &'a mut Self::Output;
}
/// An unbounded range.
#[derive(Copy)]
#[lang="full_range"]
#[unstable = "API still in development"]
pub struct FullRange;
/// A (half-open) range which is bounded at both ends.
#[derive(Copy)]
#[lang="range"]
#[unstable = "API still in development"]
pub struct Range<Idx> {
/// The lower bound of the range (inclusive).
pub start: Idx,
/// The upper bound of the range (exclusive).
pub end: Idx,
}
#[unstable = "API still in development"]
impl<Idx: Clone + Step> Iterator for Range<Idx> {
type Item = Idx;
#[inline]
fn next(&mut self) -> Option<Idx> {
if self.start < self.end {
let result = self.start.clone();
self.start.step();
return Some(result);
}
return None;
}
#[inline]
fn size_hint(&self) -> (uint, Option<uint>) {
if let Some(hint) = Step::steps_between(&self.start, &self.end) {
(hint, Some(hint))
} else {
(0, None)
}
}
}
#[unstable = "API still in development"]
impl<Idx: Clone + Step> DoubleEndedIterator for Range<Idx> {
#[inline]
fn next_back(&mut self) -> Option<Idx> {
if self.start < self.end {
self.end.step_back();
return Some(self.end.clone());
}
return None;
}
}
#[unstable = "API still in development"]
impl<Idx: Clone + Step> ExactSizeIterator for Range<Idx> {}
/// A range which is only bounded below.
#[derive(Copy)]
#[lang="range_from"]
#[unstable = "API still in development"]
pub struct RangeFrom<Idx> {
/// The lower bound of the range (inclusive).
pub start: Idx,
}
#[unstable = "API still in development"]
impl<Idx: Clone + Step> Iterator for RangeFrom<Idx> {
type Item = Idx;
#[inline]
fn next(&mut self) -> Option<Idx> {
// Deliberately overflow so we loop forever.
let result = self.start.clone();
self.start.step();
return Some(result);
}
}
/// A range which is only bounded above.
#[derive(Copy)]
#[lang="range_to"]
#[unstable = "API still in development"]
pub struct RangeTo<Idx> {
/// The upper bound of the range (exclusive).
pub end: Idx,
}
/// 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.
///
/// ```
/// #![feature(associated_types)]
///
/// use std::ops::Deref;
///
/// struct DerefExample<T> {
/// value: T
/// }
///
/// impl<T> Deref for DerefExample<T> {
/// type Target = T;
///
/// fn deref<'a>(&'a self) -> &'a T {
/// &self.value
/// }
/// }
///
/// fn main() {
/// let x = DerefExample { value: 'a' };
/// assert_eq!('a', *x);
/// }
/// ```
#[lang="deref"]
#[stable]
pub trait Deref {
#[stable]
type Target: ?Sized;
/// The method called to dereference a value
#[stable]
fn deref<'a>(&'a self) -> &'a Self::Target;
}
#[stable]
impl<'a, T: ?Sized> Deref for &'a T {
type Target = T;
fn deref(&self) -> &T { *self }
}
#[stable]
impl<'a, T: ?Sized> Deref for &'a mut T {
type Target = 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.
///
/// ```
/// #![feature(associated_types)]
///
/// use std::ops::{Deref, DerefMut};
///
/// struct DerefMutExample<T> {
/// value: T
/// }
///
/// impl<T> Deref for DerefMutExample<T> {
/// type Target = T;
///
/// fn deref<'a>(&'a self) -> &'a T {
/// &self.value
/// }
/// }
///
/// impl<T> DerefMut 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"]
#[stable]
pub trait DerefMut: Deref {
/// The method called to mutably dereference a value
#[stable]
fn deref_mut<'a>(&'a mut self) -> &'a mut Self::Target;
}
#[stable]
impl<'a, T: ?Sized> DerefMut 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"]
#[unstable = "uncertain about variadic generics, input versus associated types"]
pub trait Fn<Args,Result> {
/// 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"]
#[unstable = "uncertain about variadic generics, input versus associated types"]
pub trait FnMut<Args,Result> {
/// 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"]
#[unstable = "uncertain about variadic generics, input versus associated types"]
pub trait FnOnce<Args,Result> {
/// This is called when the call operator is used.
extern "rust-call" fn call_once(self, args: Args) -> Result;
}
impl<F: ?Sized, 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)
}
}