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// Copyright (c) 2015, the Dart project authors. Please see the AUTHORS file
// for details. All rights reserved. Use of this source code is governed by a
// BSD-style license that can be found in the LICENSE file.
import "package:expect/expect.dart";
import "dart:math" show pow;
var smallNumber = 1234567890; // is 31-bit integer.
var mediumNumber = 1234567890123456; // is 53-bit integer
testModPow() {
test(x, e, m, expectedResult) {
// Check that expected result is correct, using an unoptimized version.
assert(() {
if (1 is double) return true; // Don't have bignums.
slowModPow(x, e, m) {
var r = 1;
while (e > 0) {
if (e.isOdd) r = (r * x) % m as int;
e >>= 1;
x = (x * x) % m;
}
return r;
}
return slowModPow(x, e, m) == expectedResult;
}());
var result = x.modPow(e, m);
Expect.equals(expectedResult, result, "$x.modPow($e, $m)");
}
test(10, 20, 1, 0);
test(1234567890, 1000000001, 19, 11);
test(1234567890, 19, 1000000001, 122998977);
test(19, 1234567890, 1000000001, 619059596);
test(19, 1000000001, 1234567890, 84910879);
test(1000000001, 19, 1234567890, 872984351);
test(1000000001, 1234567890, 19, 0);
}
testModInverse() {
test(x, m, expectedResult) {
//print("$x op $m == $expectedResult");
// Check that expectedResult is an inverse.
assert(expectedResult < m);
// The 1 % m handles the m = 1 special case.
// This test may overflow if we don't have bignums, so only run on VM.
assert(1 is double || (((x % m) * expectedResult) - 1) % m == 0);
var result = x.modInverse(m);
Expect.equals(expectedResult, result, "$x modinv $m");
if (x > m) {
x = x % m;
var result = x.modInverse(m);
Expect.equals(expectedResult, result, "$x modinv $m");
}
}
testThrows(x, m) {
// Throws if not co-prime, which is a symmetric property.
Expect.throws(() => x.modInverse(m));
Expect.throws(() => m.modInverse(x));
}
test(1, 1, 0);
testThrows(0, 1000000001);
testThrows(2, 4);
testThrows(99, 9);
testThrows(19, 1000000001);
// Co-prime numbers
test(1234567890, 19, 11);
test(1234567890, 1000000001, 189108911);
test(19, 1234567890, 519818059);
test(1000000001, 1234567890, 1001100101);
test(12345, 12346, 12345);
test(12345, 12346, 12345);
test(smallNumber, 137, 42);
test(137, smallNumber, 856087223);
test(mediumNumber, 137, 77);
test(137, mediumNumber, 540686667207353);
}
testGcd() {
// Call testFunc with all combinations and orders of plus/minus
// value and other.
callCombos(value, other, testFunc) {
testFunc(value, other);
testFunc(value, -other);
testFunc(-value, other);
testFunc(-value, -other);
if (value == other) return;
testFunc(other, value);
testFunc(other, -value);
testFunc(-other, value);
testFunc(-other, -value);
}
// Test that gcd of value and other (non-negative) is expectedResult.
// Tests all combinations of positive and negative values and order of
// operands, so use positive values and order is not important.
test(value, other, expectedResult) {
// Check for bug in test.
assert(expectedResult == 0 || value % expectedResult == 0);
assert(expectedResult == 0 || other % expectedResult == 0);
callCombos(value, other, (a, b) {
var result = a.gcd(b);
/// Check that the result is a divisor.
Expect.equals(0, result == 0 ? a : a % result, "$result | $a");
Expect.equals(0, result == 0 ? b : b % result, "$result | $b");
// Check for bug in test. If assert fails, the expected value is too low,
// and the gcd call has found a greater common divisor.
assert(result >= expectedResult);
Expect.equals(expectedResult, result, "$a.gcd($b)");
});
}
// Test that gcd of value and other (non-negative) throws.
testThrows(value, other) {
callCombos(value, other, (a, b) {
Expect.throws(() => a.gcd(b));
});
}
testThrows(2.5, 5); // Not a method on double.
testThrows(5, 2.5); // Not accepting non-int arguments.
// Format:
// test(value1, value2, expectedResult);
test(1, 1, 1); // both are 1
test(1, 2, 1); // one is 1
test(3, 5, 1); // coprime.
test(37, 37, 37); // Same larger prime.
test(9999, 7272, 909); // Larger numbers
test(0, 1000, 1000); // One operand is zero.
test(0, 0, 0); // Both operands are zero.
// Multiplying both operands by a number multiplies result by same number.
test(693, 609, 21);
test(693 << 5, 609 << 5, 21 << 5);
test(693 * 937, 609 * 937, 21 * 937);
test(693 * pow(2, 32), 609 * pow(2, 32), 21 * pow(2, 32));
test(693 * pow(2, 52), 609 * pow(2, 52), 21 * pow(2, 52));
test(693 * pow(2, 53), 609 * pow(2, 53), 21 * pow(2, 53)); // Regression.
test(693 * pow(2, 99), 609 * pow(2, 99), 21 * pow(2, 99));
test(1234567890, 19, 1);
test(1234567890, 1000000001, 1);
test(19, 1000000001, 19);
test(0x3FFFFFFF, 0x3FFFFFFF, 0x3FFFFFFF);
test(0x3FFFFFFF, 0x40000000, 1);
test(pow(2, 54), pow(2, 53), pow(2, 53));
test((pow(2, 52) - 1) * pow(2, 10), (pow(2, 26) - 1) * pow(2, 22),
(pow(2, 26) - 1) * pow(2, 10));
}
main() {
testModPow(); // //# modPow: ok
testModInverse();
testGcd();
}