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// Copyright © 2024 Mikhail Hogrefe
//
// This file is part of Malachite.
//
// Malachite is free software: you can redistribute it and/or modify it under the terms of the GNU
// Lesser General Public License (LGPL) as published by the Free Software Foundation; either version
// 3 of the License, or (at your option) any later version. See <https://www.gnu.org/licenses/>.
use crate::integer::Integer;
use core::cmp::Ordering;
use malachite_base::num::conversion::traits::{ConvertibleFrom, RoundingFrom};
use malachite_base::rounding_modes::RoundingMode;
#[derive(Clone, Copy, Debug, Eq, PartialEq)]
pub struct PrimitiveFloatFromIntegerError;
macro_rules! float_impls {
($f: ident) => {
impl<'a> RoundingFrom<&'a Integer> for $f {
/// Converts an [`Integer`] to a primitive float according to a specified
/// [`RoundingMode`]. An [`Ordering`] is also returned, indicating whether the returned
/// value is less than, equal to, or greater than the original value.
///
/// - If the rounding mode is `Floor` the largest float less than or equal to the
/// [`Integer`] is returned. If the [`Integer`] is greater than the maximum finite
/// float, then the maximum finite float is returned. If it is smaller than the
/// minimum finite float, then negative infinity is returned.
/// - If the rounding mode is `Ceiling`, the smallest float greater than or equal to the
/// [`Integer`] is returned. If the [`Integer`] is greater than the maximum finite
/// float, then positive infinity is returned. If it is smaller than the minimum
/// finite float, then the minimum finite float is returned.
/// - If the rounding mode is `Down`, then the rounding proceeds as with `Floor` if the
/// [`Integer`] is non-negative and as with `Ceiling` if the [`Integer`] is negative.
/// - If the rounding mode is `Up`, then the rounding proceeds as with `Ceiling` if the
/// [`Integer`] is non-negative and as with `Floor` if the [`Integer`] is negative.
/// - If the rounding mode is `Nearest`, then the nearest float is returned. If the
/// [`Integer`] is exactly between two floats, the float with the zero
/// least-significant bit in its representation is selected. If the [`Integer`] is
/// greater than the maximum finite float, then the maximum finite float is returned.
///
/// # Worst-case complexity
/// $T(n) = O(n)$
///
/// $M(n) = O(1)$
///
/// where $T$ is time, $M$ is additional memory, and $n$ is `value.significant_bits()`.
///
/// # Panics
/// Panics if the rounding mode is `Exact` and `value` cannot be represented exactly.
///
/// # Examples
/// See [here](super::primitive_float_from_integer#rounding_from).
fn rounding_from(value: &'a Integer, rm: RoundingMode) -> ($f, Ordering) {
if value.sign {
$f::rounding_from(&value.abs, rm)
} else {
let (f, o) = $f::rounding_from(&value.abs, -rm);
(-f, o.reverse())
}
}
}
impl<'a> TryFrom<&'a Integer> for $f {
type Error = PrimitiveFloatFromIntegerError;
/// Converts an [`Integer`] to a primitive float.
///
/// If the input isn't exactly equal to some float, an error is returned.
///
/// # Worst-case complexity
/// $T(n) = O(n)$
///
/// $M(n) = O(1)$
///
/// where $T$ is time, $M$ is additional memory, and $n$ is `value.significant_bits()`.
///
/// # Examples
/// See [here](super::primitive_float_from_integer#try_from).
fn try_from(value: &'a Integer) -> Result<$f, Self::Error> {
$f::try_from(&value.abs)
.map(|f| if value.sign { f } else { -f })
.map_err(|_| PrimitiveFloatFromIntegerError)
}
}
impl<'a> ConvertibleFrom<&'a Integer> for $f {
/// Determines whether an [`Integer`] can be exactly converted to a primitive float.
///
/// # Worst-case complexity
/// $T(n) = O(n)$
///
/// $M(n) = O(1)$
///
/// where $T$ is time, $M$ is additional memory, and $n$ is `value.significant_bits()`.
///
/// # Examples
/// See [here](super::primitive_float_from_integer#convertible_from).
fn convertible_from(value: &'a Integer) -> bool {
$f::convertible_from(&value.abs)
}
}
};
}
apply_to_primitive_floats!(float_impls);