b78b749810
This commit changes the ToStr trait to:
impl<T: fmt::Show> ToStr for T {
fn to_str(&self) -> ~str { format!("{}", *self) }
}
The ToStr trait has been on the chopping block for quite awhile now, and this is
the final nail in its coffin. The trait and the corresponding method are not
being removed as part of this commit, but rather any implementations of the
`ToStr` trait are being forbidden because of the generic impl. The new way to
get the `to_str()` method to work is to implement `fmt::Show`.
Formatting into a `&mut Writer` (as `format!` does) is much more efficient than
`ToStr` when building up large strings. The `ToStr` trait forces many
intermediate allocations to be made while the `fmt::Show` trait allows
incremental buildup in the same heap allocated buffer. Additionally, the
`fmt::Show` trait is much more extensible in terms of interoperation with other
`Writer` instances and in more situations. By design the `ToStr` trait requires
at least one allocation whereas the `fmt::Show` trait does not require any
allocations.
Closes #8242
Closes #9806
61 lines
1.7 KiB
Rust
61 lines
1.7 KiB
Rust
// Copyright 2012-2013 The Rust Project Developers. See the COPYRIGHT
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// file at the top-level directory of this distribution and at
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// http://rust-lang.org/COPYRIGHT.
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//
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// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
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// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
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// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
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// option. This file may not be copied, modified, or distributed
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// except according to those terms.
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/*!
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The `ToStr` trait for converting to strings
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*/
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use fmt;
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/// A generic trait for converting a value to a string
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pub trait ToStr {
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/// Converts the value of `self` to an owned string
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fn to_str(&self) -> ~str;
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}
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/// Trait for converting a type to a string, consuming it in the process.
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pub trait IntoStr {
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/// Consume and convert to a string.
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fn into_str(self) -> ~str;
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}
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impl<T: fmt::Show> ToStr for T {
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fn to_str(&self) -> ~str { format!("{}", *self) }
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}
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#[cfg(test)]
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mod tests {
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use super::*;
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#[test]
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fn test_simple_types() {
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assert_eq!(1i.to_str(), ~"1");
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assert_eq!((-1i).to_str(), ~"-1");
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assert_eq!(200u.to_str(), ~"200");
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assert_eq!(2u8.to_str(), ~"2");
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assert_eq!(true.to_str(), ~"true");
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assert_eq!(false.to_str(), ~"false");
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assert_eq!(().to_str(), ~"()");
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assert_eq!((~"hi").to_str(), ~"hi");
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}
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#[test]
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fn test_vectors() {
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let x: ~[int] = ~[];
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assert_eq!(x.to_str(), ~"[]");
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assert_eq!((~[1]).to_str(), ~"[1]");
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assert_eq!((~[1, 2, 3]).to_str(), ~"[1, 2, 3]");
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assert!((~[~[], ~[1], ~[1, 1]]).to_str() ==
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~"[[], [1], [1, 1]]");
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}
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}
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