Add BigInteger::mod()

brick · Jan 21, 2020 · 73f3ca7 · 73f3ca7
1 parent 32e67c9
commit 73f3ca7
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diff --git a/src/BigInteger.php b/src/BigInteger.php
@@ -369,6 +369,8 @@ public function quotient($that) : BigInteger
     /**
      * Returns the remainder of the division of this number by the given one.
      *
+     * The remainder, when non-zero, has the same sign as the dividend.
+     *
      * @param BigNumber|number|string $that The divisor. Must be convertible to a BigInteger.
      *
      * @return BigInteger
@@ -413,6 +415,31 @@ public function quotientAndRemainder($that) : array
         ];
     }
 
+    /**
+     * Returns the modulo of this number and the given one.
+     *
+     * The modulo operation yields the same result as the remainder operation when both operands are of the same sign,
+     * and may differ when signs are different.
+     *
+     * The result of the modulo operation, when non-zero, has the same sign as the divisor.
+     *
+     * @param BigNumber|number|string $that The divisor. Must be convertible to a BigInteger.
+     *
+     * @return BigInteger
+     *
+     * @throws DivisionByZeroException If the divisor is zero.
+     */
+    public function mod($that) : BigInteger
+    {
+        $that = BigInteger::of($that);
+
+        if ($that->value === '0') {
+            throw DivisionByZeroException::divisionByZero();
+        }
+
+        return $this->remainder($that)->plus($that)->remainder($that);
+    }
+
     /**
      * Returns the greatest common divisor of this number and the given one.
      *

diff --git a/tests/BigIntegerTest.php b/tests/BigIntegerTest.php
@@ -1239,6 +1239,8 @@ public function providerQuotientAndRemainder()
             ['-1', '123', '0', '-1'],
             ['-1', '-123', '0', '-1'],
 
+            ['-21', '4', '-5', '-1'],
+
             ['1999999999999999999999999', '2000000000000000000000000', '0', '1999999999999999999999999'],
             ['1999999999999999999999999', '-2000000000000000000000000', '0', '1999999999999999999999999'],
             ['-1999999999999999999999999', '2000000000000000000000000', '0', '-1999999999999999999999999'],
@@ -1299,6 +1301,103 @@ public function testQuotientAndRemainderByZeroThrowsException()
         BigInteger::of(1)->quotientAndRemainder(0);
     }
 
+    /**
+     * @dataProvider providerMod
+     */
+    public function testMod(string $dividend, string $divisor, string $expected) : void
+    {
+        $this->assertBigIntegerEquals($expected, BigInteger::of($dividend)->mod($divisor));
+    }
+
+    public function providerMod() : array
+    {
+        return [
+            ['0', '1', '0'],
+            ['0', '-1', '0'],
+
+            ['1', '123', '1'],
+            ['1', '-123', '-122'],
+            ['-1', '123', '122'],
+            ['-1', '-123', '-1'],
+
+            ['2',   '7', '2'],
+            ['2',  '-7', '-5'],
+            ['-2',  '7', '5'],
+            ['-2', '-7', '-2'],
+
+            ['12',   '7', '5'],
+            ['12',  '-7', '-2'],
+            ['-12',  '7', '2'],
+            ['-12', '-7', '-5'],
+
+            ['123', '1', '0'],
+            ['123', '-1', '0'],
+            ['-123', '1', '0'],
+            ['-123', '-1', '0'],
+
+            ['123', '2', '1'],
+            ['123', '-2', '-1'],
+            ['-123', '2', '1'],
+            ['-123', '-2', '-1'],
+
+            ['123', '123', '0'],
+            ['123', '-123', '0'],
+            ['-123', '123', '0'],
+            ['-123', '-123', '0'],
+
+            ['123', '124', '123'],
+            ['123', '-124', '-1'],
+            ['-123', '124', '1'],
+            ['-123', '-124', '-123'],
+
+            ['124', '123', '1'],
+            ['124', '-123', '-122'],
+            ['-124', '123', '122'],
+            ['-124', '-123', '-1'],
+
+            ['100000000', '353467', '322306'],
+            ['100000000', '-353467', '-31161'],
+            ['-100000000', '353467', '31161'],
+            ['-100000000', '-353467', '-322306'],
+
+            ['1999999999999999999999999', '2000000000000000000000000', '1999999999999999999999999'],
+            ['1999999999999999999999999', '-2000000000000000000000000', '-1'],
+            ['-1999999999999999999999999', '2000000000000000000000000', '1'],
+            ['-1999999999999999999999999', '-2000000000000000000000000', '-1999999999999999999999999'],
+
+            ['1000000000000000000000000000000',   '3',   '1'],
+            ['1000000000000000000000000000000',  '-3',  '-2'],
+            ['1000000000000000000000000000000',   '9',   '1'],
+            ['1000000000000000000000000000000',  '-9',  '-8'],
+            ['1000000000000000000000000000000',  '11',   '1'],
+            ['1000000000000000000000000000000', '-11', '-10'],
+            ['1000000000000000000000000000000',  '13',   '1'],
+            ['1000000000000000000000000000000', '-13', '-12'],
+            ['1000000000000000000000000000000',  '21',   '1'],
+            ['1000000000000000000000000000000', '-21', '-20'],
+
+            ['123456789123456789123456789', '987654321987654321', '850308642973765431'],
+            ['123456789123456789123456789', '-87654321987654321', '-22030924930968528'],
+            ['-123456789123456789123456789', '7654321987654321', '5820145655913952'],
+            ['-123456789123456789123456789', '-654321987654321', '-205094497790673'],
+
+            ['123456789098765432101234567890987654321', '1', '0'],
+            ['123456789098765432101234567890987654321', '-1', '0'],
+            ['1282493059039502950823948435791053205342314', '24342491090593053', '4167539367989094'],
+            ['1000000000000000000000000000000000000000000000', '7777777777777777', '2232222222222222'],
+            ['999999999999999999999999999999999999999999999', '22221222222', '13737242865'],
+            ['49283205308081983923480483094304390249024223', '-23981985358744892239240813', '-3262726521512570595385995'],
+            ['-8378278174814983902084304176539029302438924', '384758527893793829309012129991', '17174256549949655473639464372'],
+            ['-444444444444444444444444444444444444411111', '-33333333333333', '-33333333300000'],
+        ];
+    }
+
+    public function testModZeroThrowsException() : void
+    {
+        $this->expectException(DivisionByZeroException::class);
+        BigInteger::of(1)->mod(0);
+    }
+
     /**
      * @dataProvider providerPower
      *