fixed-bigint 0.2.5

// Copyright 2021 Google LLC
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//      http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

//! Absolute difference implementation for FixedUInt.

use super::{FixedUInt, MachineWord};
use crate::const_numtraits::ConstAbsDiff;
use crate::machineword::ConstMachineWord;

c0nst::c0nst! {
    impl<T: [c0nst] ConstMachineWord + MachineWord, const N: usize> c0nst ConstAbsDiff for FixedUInt<T, N> {
        fn abs_diff(self, other: Self) -> Self {
            if self >= other {
                self - other
            } else {
                other - self
            }
        }
    }
}

#[cfg(test)]
mod tests {
    use super::*;

    #[test]
    fn test_abs_diff() {
        type U16 = FixedUInt<u8, 2>;

        assert_eq!(
            ConstAbsDiff::abs_diff(U16::from(10u8), U16::from(3u8)),
            U16::from(7u8)
        );
        assert_eq!(
            ConstAbsDiff::abs_diff(U16::from(3u8), U16::from(10u8)),
            U16::from(7u8)
        );
        assert_eq!(
            ConstAbsDiff::abs_diff(U16::from(5u8), U16::from(5u8)),
            U16::from(0u8)
        );
        assert_eq!(
            ConstAbsDiff::abs_diff(U16::from(0u8), U16::from(100u8)),
            U16::from(100u8)
        );
        assert_eq!(
            ConstAbsDiff::abs_diff(U16::from(255u8), U16::from(0u8)),
            U16::from(255u8)
        );
    }

    c0nst::c0nst! {
        pub c0nst fn const_abs_diff<T: [c0nst] ConstMachineWord + MachineWord, const N: usize>(
            a: FixedUInt<T, N>,
            b: FixedUInt<T, N>,
        ) -> FixedUInt<T, N> {
            ConstAbsDiff::abs_diff(a, b)
        }
    }

    #[test]
    fn test_const_abs_diff() {
        type U16 = FixedUInt<u8, 2>;

        assert_eq!(
            const_abs_diff(U16::from(10u8), U16::from(3u8)),
            U16::from(7u8)
        );

        #[cfg(feature = "nightly")]
        {
            const A: U16 = FixedUInt { array: [10, 0] };
            const B: U16 = FixedUInt { array: [3, 0] };
            const DIFF: U16 = const_abs_diff(A, B);
            assert_eq!(DIFF, FixedUInt { array: [7, 0] });
        }
    }
}