rust/src/libcore/clone.rs

// Copyright 2012-2013 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.

/*! The Clone trait for types that cannot be "implicitly copied"

In Rust, some simple types are "implicitly copyable" and when you
assign them or pass them as arguments, the receiver will get a copy,
leaving the original value in place. These types do not require
allocation to copy and do not have finalizers (i.e. they do not
contain owned boxes or implement `Drop`), so the compiler considers
them cheap and safe to copy and automatically implements the `Copy`
trait for them. For other types copies must be made explicitly,
by convention implementing the `Clone` trait and calling the
`clone` method.

*/

pub trait Clone {
    /// Return a deep copy of the owned object tree. Managed boxes are cloned with a shallow copy.
    fn clone(&self) -> Self;
}

impl Clone for () {
    /// Return a copy of the value.
    #[inline(always)]
    fn clone(&self) -> () { () }
}

impl<T:Clone> Clone for ~T {
    /// Return a deep copy of the owned box.
    #[inline(always)]
    fn clone(&self) -> ~T { ~(**self).clone() }
}

impl<T> Clone for @T {
    /// Return a shallow copy of the managed box.
    #[inline(always)]
    fn clone(&self) -> @T { *self }
}

impl<T> Clone for @mut T {
    /// Return a shallow copy of the managed box.
    #[inline(always)]
    fn clone(&self) -> @mut T { *self }
}

macro_rules! clone_impl(
    ($t:ty) => {
        impl Clone for $t {
            /// Return a copy of the value.
            #[inline(always)]
            fn clone(&self) -> $t { *self }
        }
    }
)

clone_impl!(int)
clone_impl!(i8)
clone_impl!(i16)
clone_impl!(i32)
clone_impl!(i64)

clone_impl!(uint)
clone_impl!(u8)
clone_impl!(u16)
clone_impl!(u32)
clone_impl!(u64)

clone_impl!(float)
clone_impl!(f32)
clone_impl!(f64)

clone_impl!(bool)
clone_impl!(char)

#[test]
fn test_owned_clone() {
    let a: ~int = ~5i;
    let b: ~int = a.clone();
    assert!(a == b);
}

#[test]
fn test_managed_clone() {
    let a: @int = @5i;
    let b: @int = a.clone();
    assert!(a == b);
}

#[test]
fn test_managed_mut_clone() {
    let a: @mut int = @mut 5i;
    let b: @mut int = a.clone();
    assert!(a == b);
    *b = 10;
    assert!(a == b);
}