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use malachite_base::num::basic::traits::One;
use malachite_nz::natural::Natural;
use std::str::FromStr;
use Rational;
impl FromStr for Rational {
type Err = ();
/// Converts an string to a [`Rational`].
///
/// If the string does not represent a valid [`Rational`], an `Err` is returned. The numerator
/// and denominator do not need to be in lowest terms, but the denominator must be nonzero. A
/// negative sign is only allowed at the 0th position of the string.
///
/// # Worst-case complexity
/// $T(n) = O(n (\log n)^2 \log\log n)$
///
/// $M(n) = O(n \log n)$
///
/// where $T$ is time, $M$ is additional memory, and $n$ is `s.len()`.
///
/// # Examples
/// ```
/// use malachite_q::Rational;
/// use std::str::FromStr;
///
/// assert_eq!(Rational::from_str("123456").unwrap(), 123456);
/// assert_eq!(Rational::from_str("00123456").unwrap(), 123456);
/// assert_eq!(Rational::from_str("0").unwrap(), 0);
/// assert_eq!(Rational::from_str("-123456").unwrap(), -123456);
/// assert_eq!(Rational::from_str("-00123456").unwrap(), -123456);
/// assert_eq!(Rational::from_str("-0").unwrap(), 0);
/// assert_eq!(Rational::from_str("22/7").unwrap().to_string(), "22/7");
/// assert_eq!(Rational::from_str("01/02").unwrap().to_string(), "1/2");
/// assert_eq!(Rational::from_str("3/21").unwrap().to_string(), "1/7");
/// assert_eq!(Rational::from_str("-22/7").unwrap().to_string(), "-22/7");
/// assert_eq!(Rational::from_str("-01/02").unwrap().to_string(), "-1/2");
/// assert_eq!(Rational::from_str("-3/21").unwrap().to_string(), "-1/7");
///
/// assert!(Rational::from_str("").is_err());
/// assert!(Rational::from_str("a").is_err());
/// assert!(Rational::from_str("1/0").is_err());
/// assert!(Rational::from_str("/1").is_err());
/// assert!(Rational::from_str("1/").is_err());
/// assert!(Rational::from_str("--1").is_err());
/// assert!(Rational::from_str("1/-2").is_err());
/// ```
#[inline]
fn from_str(s: &str) -> Result<Rational, ()> {
let (abs_string, sign) = if let Some(abs_string) = s.strip_prefix('-') {
(abs_string, false)
} else {
(s, true)
};
let numerator;
let denominator;
if let Some(slash_index) = abs_string.find('/') {
numerator = Natural::from_str(&abs_string[..slash_index])?;
denominator = Natural::from_str(&abs_string[slash_index + 1..])?;
if denominator == 0u32 {
return Err(());
}
} else {
numerator = Natural::from_str(abs_string)?;
denominator = Natural::ONE;
}
Ok(Rational::from_sign_and_naturals(
sign,
numerator,
denominator,
))
}
}