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Add Show and Clone trait to arrays #18951

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Nov 18, 2014
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Add Show and Clone trait to arrays #18951

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30 changes: 22 additions & 8 deletions src/libcore/array.rs
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Expand Up @@ -8,22 +8,36 @@
// option. This file may not be copied, modified, or distributed
// except according to those terms.

/*!
* Implementations of things like `Eq` for fixed-length arrays
* up to a certain length. Eventually we should able to generalize
* to all lengths.
*/
//! Implementations of things like `Eq` for fixed-length arrays
//! up to a certain length. Eventually we should able to generalize
//! to all lengths.

#![stable]
#![experimental] // not yet reviewed

use cmp::*;
use option::{Option};
use clone::Clone;
use cmp::{PartialEq, Eq, PartialOrd, Ord, Ordering};
use fmt;
use kinds::Copy;
use option::Option;

// macro for implementing n-ary tuple functions and operations
macro_rules! array_impls {
($($N:expr)+) => {
$(
#[unstable = "waiting for Clone to stabilize"]
impl<T:Copy> Clone for [T, ..$N] {
fn clone(&self) -> [T, ..$N] {
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You should be able to implement for non-Copy Ts unsafely:

fn clone(&self) -> [T, ..$N] {
    let mut cloned: [T, ..$N] = unsafe { mem::zeroed() };
    for i in range(0, $N) {
        cloned[i] = x[i].clone();
    }
    cloned
}

I think this is safe with regards to destructors and clone() failing but someone else should confirm. :-)

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That's not safe because clone can throw, and calling a destructor on zeroed memory is not well-defined. Drop flags are an implementation detail and removing them is planned. It is possible to write this code correctly, but you need to handle the unwinding case manually.

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Exceptions are just plain awful.

*self
}
}

#[unstable = "waiting for Show to stabilize"]
impl<T:fmt::Show> fmt::Show for [T, ..$N] {
fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
fmt::Show::fmt(&self[], f)
}
}

#[unstable = "waiting for PartialEq to stabilize"]
impl<T:PartialEq> PartialEq for [T, ..$N] {
#[inline]
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