Implement num_integer::Integer (#20)

* Add num_integer dep #19

* Quick implementation of Integer easy parts #19

* Add gcd/lcm, tests for Integer divisions

* Add basic gcd/lcm tests

* Bump version number

Author: kaidokert

Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "fixed-bigint"
-version = "0.1.5"
+version = "0.1.6"
 authors = ["kaidokert <[email protected]>"]
 documentation = "https://docs.rs/fixed-bigint"
 edition = "2018"
@@ -20,6 +20,10 @@ exclude = ["/.github/*"]
 version = "0.2.14"
 default-features = false
 
+[dependencies.num-integer]
+version = "0.1.44"
+default-features = false
+
 [profile.dev]
 opt-level = 0
 debug = true

README.md

@@ -17,6 +17,8 @@ The crate is written for `no_std` and `no_alloc` environments with option for pa
 
 The arithmetic operands ( +, -, .add() ) panic on overflow, just like native integer types. Panic-free alternatives like `overlowing_add` and `wrapping_add` are supported.
 
+In addition to basic arithmetic, two main traits are implemented: [num_traits::PrimInt](https://docs.rs/num-traits/latest/num_traits/int/trait.PrimInt.html) and [num_integer::Integer](https://docs.rs/num/latest/num/integer/trait.Integer.html).
+
 _TODO list_:
  * Implement experimental `unchecked_math` operands, unchecked_mul, unchecked_div etc.
  * Probably needs its own error structs instead of reusing core::fmt::Error and core::num::ParseIntError

src/fixeduint.rs

@@ -15,6 +15,8 @@
 use num_traits::ops::overflowing::{OverflowingAdd, OverflowingMul, OverflowingSub};
 use num_traits::{Bounded, One, PrimInt, ToPrimitive, Zero};
 
+use num_integer;
+
 use core::convert::TryFrom;
 use core::fmt::Write;
 
@@ -1248,6 +1250,70 @@ impl<T: MachineWord, const N: usize> num_traits::PrimInt for FixedUInt<T, N> {
 
 // #endregion unimplemented
 
+// #region num-integer::Integer
+
+// Most code here from num_integer crate, unsigned implementation
+
+impl<T: MachineWord, const N: usize> num_integer::Integer for FixedUInt<T, N> {
+    fn div_floor(&self, other: &Self) -> Self {
+        *self / *other
+    }
+    fn mod_floor(&self, other: &Self) -> Self {
+        *self % *other
+    }
+    fn gcd(&self, other: &Self) -> Self {
+        // Use Stein's algorithm
+        let mut m = *self;
+        let mut n = *other;
+        let zero = Self::zero();
+        if m == zero || n == zero {
+            return m | n;
+        }
+
+        // find common factors of 2
+        let shift = (m | n).trailing_zeros();
+
+        // divide n and m by 2 until odd
+        m = m >> m.trailing_zeros();
+        n = n >> n.trailing_zeros();
+
+        while m != n {
+            if m > n {
+                m -= n;
+                m = m >> m.trailing_zeros();
+            } else {
+                n -= m;
+                n = n >> n.trailing_zeros();
+            }
+        }
+        m << shift
+    }
+    fn lcm(&self, other: &Self) -> Self {
+        if self.is_zero() && other.is_zero() {
+            return Self::zero();
+        }
+        let gcd = self.gcd(other);
+        *self * (*other / gcd)
+    }
+    fn divides(&self, other: &Self) -> bool {
+        self.is_multiple_of(other)
+    }
+    fn is_multiple_of(&self, other: &Self) -> bool {
+        (*self) % other == Self::zero()
+    }
+    fn is_even(&self) -> bool {
+        (*self) & Self::one() == Self::zero()
+    }
+    fn is_odd(&self) -> bool {
+        !self.is_even()
+    }
+    fn div_rem(&self, other: &Self) -> (Self, Self) {
+        self.div_rem(other)
+    }
+}
+
+// #endregion num-integer::Integer
+
 #[cfg(test)]
 mod tests {
     use super::FixedUInt as Bn;

tests/integer.rs

@@ -0,0 +1,94 @@
+// 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.
+
+#[cfg(test)]
+use fixed_bigint::FixedUInt;
+use num_integer::Integer;
+
+#[test]
+fn test_evenodd() {
+    fn even_odd<T: num_integer::Integer + From<u8>>() {
+        let tests = [(0u8, true), (1u8, false), (2u8, true), (255u8, false)];
+        for &(num, even) in &tests {
+            let f: T = num.into();
+            assert_eq!(f.is_even(), even);
+            assert_eq!(f.is_odd(), !even);
+        }
+    }
+    even_odd::<u8>();
+    even_odd::<FixedUInt<u8, 1>>();
+    even_odd::<FixedUInt<u8, 2>>();
+    even_odd::<FixedUInt<u16, 1>>();
+}
+
+#[test]
+fn test_divides() {
+    fn divides<T: num_integer::Integer + From<u8>>() {
+        let tests = [(6u8, 3u8, true), (8, 2, true), (8, 1, true), (17, 2, false)];
+        for &(multiple, multiplier, expected) in &tests {
+            assert_eq!(multiple.is_multiple_of(&multiplier), expected);
+            assert_eq!(multiple.divides(&multiplier), expected);
+        }
+        let divrem = [
+            (6u8, 3u8, 2u8, 0u8),
+            (8, 2, 4, 0),
+            (7, 2, 3, 1),
+            (89, 13, 6, 11),
+        ];
+        for &(multiple, divider, div, rem) in &divrem {
+            let (divres, remres) = multiple.div_rem(&divider);
+            assert_eq!(divres, div);
+            assert_eq!(remres, rem);
+
+            assert_eq!(multiple.div_floor(&divider), divres);
+            assert_eq!(multiple.mod_floor(&divider), remres);
+        }
+    }
+    divides::<u8>();
+    divides::<FixedUInt<u8, 1>>();
+    divides::<FixedUInt<u8, 2>>();
+    divides::<FixedUInt<u16, 1>>();
+}
+
+// TODO: Test GCD / LCM
+#[test]
+fn test_gcd_lcm() {
+    fn gcd_lcm<T: num_integer::Integer + From<u8>>() {
+        let gcd_tests = [
+            (8u8, 12u8, 4u8),
+            (1, 1, 1),
+            (100, 100, 100),
+            (99, 98, 1),
+            (99, 90, 9),
+        ];
+        for &(a, b, expected) in &gcd_tests {
+            assert_eq!(a.gcd(&b), expected);
+        }
+        let lcm_tests = [
+            (10u8, 2u8, 10u8),
+            (1, 1, 1),
+            (4, 6, 12),
+            (7, 12, 84),
+            (14, 12, 84),
+            (255, 255, 255),
+        ];
+        for &(a, b, expected) in &lcm_tests {
+            assert_eq!(a.lcm(&b), expected);
+        }
+    }
+    gcd_lcm::<u8>();
+    gcd_lcm::<FixedUInt<u8, 1>>();
+    gcd_lcm::<FixedUInt<u8, 2>>();
+    gcd_lcm::<FixedUInt<u16, 1>>();
+}