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