70 lines
2.0 KiB
Rust
70 lines
2.0 KiB
Rust
// Copyright 2012 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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//! The `FromStr` trait for types that can be created from strings
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use option::{Option, Some, None};
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use string::String;
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use str::StrAllocating;
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/// A trait to abstract the idea of creating a new instance of a type from a
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/// string.
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pub trait FromStr {
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/// Parses a string `s` to return an optional value of this type. If the
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/// string is ill-formatted, the None is returned.
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fn from_str(s: &str) -> Option<Self>;
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}
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/// A utility function that just calls FromStr::from_str
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pub fn from_str<A: FromStr>(s: &str) -> Option<A> {
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FromStr::from_str(s)
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}
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impl FromStr for bool {
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/// Parse a `bool` from a string.
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///
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/// Yields an `Option<bool>`, because `s` may or may not actually be parseable.
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///
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/// # Examples
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///
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/// ```rust
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/// assert_eq!(from_str::<bool>("true"), Some(true));
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/// assert_eq!(from_str::<bool>("false"), Some(false));
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/// assert_eq!(from_str::<bool>("not even a boolean"), None);
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/// ```
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#[inline]
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fn from_str(s: &str) -> Option<bool> {
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match s {
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"true" => Some(true),
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"false" => Some(false),
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_ => None,
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}
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}
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}
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impl FromStr for String {
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#[inline]
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fn from_str(s: &str) -> Option<String> {
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Some(s.to_string())
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}
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}
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#[cfg(test)]
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mod test {
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use prelude::*;
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#[test]
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fn test_bool_from_str() {
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assert_eq!(from_str::<bool>("true"), Some(true));
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assert_eq!(from_str::<bool>("false"), Some(false));
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assert_eq!(from_str::<bool>("not even a boolean"), None);
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}
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}
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