Merge #245

245: Implement Euclid division and remainder r=cuviper a=jaybosamiya

Now that a common trait for this has been sorted out (rust-num/num-traits#159 implemented and merged in rust-num/num-traits#195), we can now close #146 by implementing the trait for `BigInt`s. This commit does just that.

Co-authored-by: Jay Bosamiya <[email protected]>
Co-authored-by: Josh Stone <[email protected]>

Author: 3 people

ci/test_full.sh

@@ -80,7 +80,15 @@ if rustc --version | grep -q nightly; then
 fi
 
 case "${STD_FEATURES[*]}" in
-  *serde*) cargo test --manifest-path ci/big_serde/Cargo.toml ;;&
+  *serde*) (
+      cd ci/big_serde
+      # serde_test updated to 2021 edition after this version
+      check_version 1.56.0 || (
+        cargo generate-lockfile
+        cargo update -p serde_test --precise 1.0.175
+      )
+      cargo test
+    ) ;;&
   *rand*) cargo test --manifest-path ci/big_rand/Cargo.toml ;;&
   *quickcheck*) (
       cd ci/big_quickcheck

src/bigint/division.rs

@@ -6,7 +6,7 @@ use crate::{IsizePromotion, UsizePromotion};
 
 use core::ops::{Div, DivAssign, Rem, RemAssign};
 use num_integer::Integer;
-use num_traits::{CheckedDiv, ToPrimitive, Zero};
+use num_traits::{CheckedDiv, CheckedEuclid, Euclid, Signed, ToPrimitive, Zero};
 
 forward_all_binop_to_ref_ref!(impl Div for BigInt, div);
 
@@ -446,3 +446,51 @@ impl CheckedDiv for BigInt {
         Some(self.div(v))
     }
 }
+
+impl CheckedEuclid for BigInt {
+    #[inline]
+    fn checked_div_euclid(&self, v: &BigInt) -> Option<BigInt> {
+        if v.is_zero() {
+            return None;
+        }
+        Some(self.div_euclid(v))
+    }
+
+    #[inline]
+    fn checked_rem_euclid(&self, v: &BigInt) -> Option<BigInt> {
+        if v.is_zero() {
+            return None;
+        }
+        Some(self.rem_euclid(v))
+    }
+}
+
+impl Euclid for BigInt {
+    #[inline]
+    fn div_euclid(&self, v: &BigInt) -> BigInt {
+        let (q, r) = self.div_rem(v);
+        if r.is_negative() {
+            if v.is_positive() {
+                q - 1
+            } else {
+                q + 1
+            }
+        } else {
+            q
+        }
+    }
+
+    #[inline]
+    fn rem_euclid(&self, v: &BigInt) -> BigInt {
+        let r = self % v;
+        if r.is_negative() {
+            if v.is_positive() {
+                r + v
+            } else {
+                r - v
+            }
+        } else {
+            r
+        }
+    }
+}

src/biguint/division.rs

@@ -10,7 +10,7 @@ use core::cmp::Ordering::{Equal, Greater, Less};
 use core::mem;
 use core::ops::{Div, DivAssign, Rem, RemAssign};
 use num_integer::Integer;
-use num_traits::{CheckedDiv, One, ToPrimitive, Zero};
+use num_traits::{CheckedDiv, CheckedEuclid, Euclid, One, ToPrimitive, Zero};
 
 /// Divide a two digit numerator by a one digit divisor, returns quotient and remainder:
 ///
@@ -618,3 +618,35 @@ impl CheckedDiv for BigUint {
         Some(self.div(v))
     }
 }
+
+impl CheckedEuclid for BigUint {
+    #[inline]
+    fn checked_div_euclid(&self, v: &BigUint) -> Option<BigUint> {
+        if v.is_zero() {
+            return None;
+        }
+        Some(self.div_euclid(v))
+    }
+
+    #[inline]
+    fn checked_rem_euclid(&self, v: &BigUint) -> Option<BigUint> {
+        if v.is_zero() {
+            return None;
+        }
+        Some(self.rem_euclid(v))
+    }
+}
+
+impl Euclid for BigUint {
+    #[inline]
+    fn div_euclid(&self, v: &BigUint) -> BigUint {
+        // trivially same as regular division
+        self / v
+    }
+
+    #[inline]
+    fn rem_euclid(&self, v: &BigUint) -> BigUint {
+        // trivially same as regular remainder
+        self % v
+    }
+}

tests/bigint.rs

@@ -14,7 +14,7 @@ use std::{u16, u32, u64, u8, usize};
 
 use num_integer::Integer;
 use num_traits::{
-    pow, FromBytes, FromPrimitive, Num, One, Pow, Signed, ToBytes, ToPrimitive, Zero,
+    pow, Euclid, FromBytes, FromPrimitive, Num, One, Pow, Signed, ToBytes, ToPrimitive, Zero,
 };
 
 mod consts;
@@ -896,6 +896,58 @@ fn test_div_ceil() {
     }
 }
 
+#[test]
+fn test_div_rem_euclid() {
+    fn check_sub(a: &BigInt, b: &BigInt, ans_d: &BigInt, ans_m: &BigInt) {
+        eprintln!("{} {} {} {}", a, b, ans_d, ans_m);
+        assert_eq!(a.div_euclid(b), *ans_d);
+        assert_eq!(a.rem_euclid(b), *ans_m);
+        assert!(*ans_m >= BigInt::zero());
+        assert!(*ans_m < b.abs());
+    }
+
+    fn check(a: &BigInt, b: &BigInt, d: &BigInt, m: &BigInt) {
+        if m.is_zero() {
+            check_sub(a, b, d, m);
+            check_sub(a, &b.neg(), &d.neg(), m);
+            check_sub(&a.neg(), b, &d.neg(), m);
+            check_sub(&a.neg(), &b.neg(), d, m);
+        } else {
+            let one: BigInt = One::one();
+            check_sub(a, b, d, m);
+            check_sub(a, &b.neg(), &d.neg(), m);
+            check_sub(&a.neg(), b, &(d + &one).neg(), &(b - m));
+            check_sub(&a.neg(), &b.neg(), &(d + &one), &(b.abs() - m));
+        }
+    }
+
+    for elm in MUL_TRIPLES.iter() {
+        let (a_vec, b_vec, c_vec) = *elm;
+        let a = BigInt::from_slice(Plus, a_vec);
+        let b = BigInt::from_slice(Plus, b_vec);
+        let c = BigInt::from_slice(Plus, c_vec);
+
+        if !a.is_zero() {
+            check(&c, &a, &b, &Zero::zero());
+        }
+        if !b.is_zero() {
+            check(&c, &b, &a, &Zero::zero());
+        }
+    }
+
+    for elm in DIV_REM_QUADRUPLES.iter() {
+        let (a_vec, b_vec, c_vec, d_vec) = *elm;
+        let a = BigInt::from_slice(Plus, a_vec);
+        let b = BigInt::from_slice(Plus, b_vec);
+        let c = BigInt::from_slice(Plus, c_vec);
+        let d = BigInt::from_slice(Plus, d_vec);
+
+        if !b.is_zero() {
+            check(&a, &b, &c, &d);
+        }
+    }
+}
+
 #[test]
 fn test_checked_add() {
     for elm in SUM_TRIPLES.iter() {

tests/biguint.rs

@@ -14,8 +14,8 @@ use std::{i128, u128};
 use std::{u16, u32, u64, u8, usize};
 
 use num_traits::{
-    pow, CheckedAdd, CheckedDiv, CheckedMul, CheckedSub, FromBytes, FromPrimitive, Num, One, Pow,
-    ToBytes, ToPrimitive, Zero,
+    pow, CheckedAdd, CheckedDiv, CheckedMul, CheckedSub, Euclid, FromBytes, FromPrimitive, Num,
+    One, Pow, ToBytes, ToPrimitive, Zero,
 };
 
 mod consts;
@@ -948,6 +948,40 @@ fn test_div_ceil() {
     }
 }
 
+#[test]
+fn test_div_rem_euclid() {
+    fn check(a: &BigUint, b: &BigUint, d: &BigUint, m: &BigUint) {
+        assert_eq!(a.div_euclid(b), *d);
+        assert_eq!(a.rem_euclid(b), *m);
+    }
+
+    for elm in MUL_TRIPLES.iter() {
+        let (a_vec, b_vec, c_vec) = *elm;
+        let a = BigUint::from_slice(a_vec);
+        let b = BigUint::from_slice(b_vec);
+        let c = BigUint::from_slice(c_vec);
+
+        if !a.is_zero() {
+            check(&c, &a, &b, &Zero::zero());
+        }
+        if !b.is_zero() {
+            check(&c, &b, &a, &Zero::zero());
+        }
+    }
+
+    for elm in DIV_REM_QUADRUPLES.iter() {
+        let (a_vec, b_vec, c_vec, d_vec) = *elm;
+        let a = BigUint::from_slice(a_vec);
+        let b = BigUint::from_slice(b_vec);
+        let c = BigUint::from_slice(c_vec);
+        let d = BigUint::from_slice(d_vec);
+
+        if !b.is_zero() {
+            check(&a, &b, &c, &d);
+        }
+    }
+}
+
 #[test]
 fn test_checked_add() {
     for elm in SUM_TRIPLES.iter() {