From 9866e500142f4974f2c21b2b29c8a89dcabe41f2 Mon Sep 17 00:00:00 2001
From: Quinton Miller <nicetas.c@gmail.com>
Date: Wed, 21 Feb 2024 18:25:38 +0800
Subject: [PATCH] Add `BigRational#%`, `#tdiv`, `#remainder` (#14306)

---
 spec/std/big/big_rational_spec.cr | 72 +++++++++++++++++++++++++++++--
 src/big/big_rational.cr           | 46 ++++++++++++++++++++
 2 files changed, 114 insertions(+), 4 deletions(-)

diff --git a/spec/std/big/big_rational_spec.cr b/spec/std/big/big_rational_spec.cr
index 7b28a4938966..0dcc75c10b87 100644
--- a/spec/std/big/big_rational_spec.cr
+++ b/spec/std/big/big_rational_spec.cr
@@ -218,10 +218,74 @@ describe BigRational do
   end
 
   it "#//" do
-    (br(10, 7) // br(3, 7)).should eq(br(9, 3))
-    expect_raises(DivisionByZeroError) { br(10, 7) / br(0, 10) }
-    (br(10, 7) // 3).should eq(0)
-    (1 // br(10, 7)).should eq(0)
+    (br(18, 7) // br(4, 5)).should eq(br(3, 1))
+    (br(-18, 7) // br(4, 5)).should eq(br(-4, 1))
+    (br(18, 7) // br(-4, 5)).should eq(br(-4, 1))
+    (br(-18, 7) // br(-4, 5)).should eq(br(3, 1))
+
+    (br(18, 5) // 2).should eq(br(1, 1))
+    (br(-18, 5) // 2).should eq(br(-2, 1))
+    (br(18, 5) // -2).should eq(br(-2, 1))
+    (br(-18, 5) // -2).should eq(br(1, 1))
+    (br(18, 5) // 2.to_big_i).should eq(br(1, 1))
+
+    expect_raises(DivisionByZeroError) { br(18, 7) // br(0, 1) }
+    expect_raises(DivisionByZeroError) { br(18, 7) // 0 }
+
+    (8 // br(10, 7)).should eq(5)
+    (-8 // br(10, 7)).should eq(-6)
+    (8 // br(-10, 7)).should eq(-6)
+    (-8 // br(-10, 7)).should eq(5)
+
+    expect_raises(DivisionByZeroError) { 8 // br(0, 7) }
+  end
+
+  it "#%" do
+    (br(18, 7) % br(4, 5)).should eq(br(6, 35))
+    (br(-18, 7) % br(4, 5)).should eq(br(22, 35))
+    (br(18, 7) % br(-4, 5)).should eq(br(-22, 35))
+    (br(-18, 7) % br(-4, 5)).should eq(br(-6, 35))
+
+    (br(18, 5) % 2).should eq(br(8, 5))
+    (br(-18, 5) % 2).should eq(br(2, 5))
+    (br(18, 5) % -2).should eq(br(-2, 5))
+    (br(-18, 5) % -2).should eq(br(-8, 5))
+    (br(18, 5) % 2.to_big_i).should eq(br(8, 5))
+
+    expect_raises(DivisionByZeroError) { br(18, 7) % br(0, 1) }
+    expect_raises(DivisionByZeroError) { br(18, 7) % 0 }
+  end
+
+  it "#tdiv" do
+    br(18, 7).tdiv(br(4, 5)).should eq(br(3, 1))
+    br(-18, 7).tdiv(br(4, 5)).should eq(br(-3, 1))
+    br(18, 7).tdiv(br(-4, 5)).should eq(br(-3, 1))
+    br(-18, 7).tdiv(br(-4, 5)).should eq(br(3, 1))
+
+    br(18, 5).tdiv(2).should eq(br(1, 1))
+    br(-18, 5).tdiv(2).should eq(br(-1, 1))
+    br(18, 5).tdiv(-2).should eq(br(-1, 1))
+    br(-18, 5).tdiv(-2).should eq(br(1, 1))
+    br(18, 5).tdiv(2.to_big_i).should eq(br(1, 1))
+
+    expect_raises(DivisionByZeroError) { br(18, 7).tdiv(br(0, 1)) }
+    expect_raises(DivisionByZeroError) { br(18, 7).tdiv(0) }
+  end
+
+  it "#remainder" do
+    br(18, 7).remainder(br(4, 5)).should eq(br(6, 35))
+    br(-18, 7).remainder(br(4, 5)).should eq(br(-6, 35))
+    br(18, 7).remainder(br(-4, 5)).should eq(br(6, 35))
+    br(-18, 7).remainder(br(-4, 5)).should eq(br(-6, 35))
+
+    br(18, 5).remainder(2).should eq(br(8, 5))
+    br(-18, 5).remainder(2).should eq(br(-8, 5))
+    br(18, 5).remainder(-2).should eq(br(8, 5))
+    br(-18, 5).remainder(-2).should eq(br(-8, 5))
+    br(18, 5).remainder(2.to_big_i).should eq(br(8, 5))
+
+    expect_raises(DivisionByZeroError) { br(18, 7).remainder(br(0, 1)) }
+    expect_raises(DivisionByZeroError) { br(18, 7).remainder(0) }
   end
 
   it "#- (negation)" do
diff --git a/src/big/big_rational.cr b/src/big/big_rational.cr
index a9466a5466a0..b14c8f4b2d4a 100644
--- a/src/big/big_rational.cr
+++ b/src/big/big_rational.cr
@@ -151,6 +151,52 @@ struct BigRational < Number
 
   Number.expand_div [BigInt, BigFloat, BigDecimal], BigRational
 
+  def //(other : BigRational) : BigRational
+    check_division_by_zero other
+    BigRational.new((numerator * other.denominator) // (denominator * other.numerator))
+  end
+
+  def //(other : Int) : BigRational
+    check_division_by_zero other
+    BigRational.new(numerator // (denominator * other))
+  end
+
+  def %(other : BigRational) : BigRational
+    check_division_by_zero other
+    BigRational.new(
+      (numerator * other.denominator) % (denominator * other.numerator),
+      denominator * other.denominator,
+    )
+  end
+
+  def %(other : Int) : BigRational
+    check_division_by_zero other
+    BigRational.new(numerator % (denominator * other), denominator)
+  end
+
+  def tdiv(other : BigRational) : BigRational
+    check_division_by_zero other
+    BigRational.new((numerator * other.denominator).tdiv(denominator * other.numerator))
+  end
+
+  def tdiv(other : Int) : BigRational
+    check_division_by_zero other
+    BigRational.new(numerator.tdiv(denominator * other))
+  end
+
+  def remainder(other : BigRational) : BigRational
+    check_division_by_zero other
+    BigRational.new(
+      (numerator * other.denominator).remainder(denominator * other.numerator),
+      denominator * other.denominator,
+    )
+  end
+
+  def remainder(other : Int) : BigRational
+    check_division_by_zero other
+    BigRational.new(numerator.remainder(denominator * other), denominator)
+  end
+
   def ceil : BigRational
     BigRational.new(-(-numerator // denominator))
   end