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abacus: bignum: add exponentiation

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This commit is contained in:
Bruno BELANYI 2021-08-21 02:33:46 +02:00
parent 0436d2e513
commit 5bc3963317
3 changed files with 127 additions and 0 deletions
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63
tests/unit/bignum.cc
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@ -267,3 +267,66 @@ TEST(BigNum, div_mod_identity) {
+ (minus_five % minus_three),
minus_five);
}
TEST(BigNum, pow_negative_exponent) {
auto const zero = BigNum(0);
auto const minus_one = BigNum(-1);
auto const three = BigNum(3);
EXPECT_EQ(pow(three, minus_one), zero);
}
TEST(BigNum, pow_zero) {
auto const zero = BigNum(0);
auto const one = BigNum(1);
auto const three = BigNum(3);
EXPECT_EQ(pow(three, zero), one);
EXPECT_EQ(pow(zero, three), zero);
EXPECT_EQ(pow(zero, zero), one); // unclear mathematically
}
TEST(BigNum, pow_one) {
auto const one = BigNum(1);
auto const three = BigNum(3);
EXPECT_EQ(pow(one, one), one);
EXPECT_EQ(pow(one, three), one);
EXPECT_EQ(pow(three, one), three);
}
TEST(BigNum, pow) {
auto const one = BigNum(1);
auto const two = BigNum(2);
auto const three = BigNum(3);
auto const four = BigNum(4);
auto const eight = BigNum(8);
auto const nine = BigNum(9);
auto const twenty_seven = BigNum(27);
auto const eighty_one = BigNum(81);
EXPECT_EQ(pow(two, two), four);
EXPECT_EQ(pow(two, three), eight);
EXPECT_EQ(pow(three, two), nine);
EXPECT_EQ(pow(three, three), twenty_seven);
EXPECT_EQ(pow(three, four), eighty_one);
}
TEST(BigNum, pow_negative) {
auto const one = BigNum(1);
auto const two = BigNum(2);
auto const minus_two = BigNum(-2);
auto const three = BigNum(3);
auto const minus_three = BigNum(-3);
auto const four = BigNum(4);
auto const minus_eight = BigNum(-8);
auto const nine = BigNum(9);
auto const minus_twenty_seven = BigNum(-27);
auto const eighty_one = BigNum(81);
EXPECT_EQ(pow(minus_two, two), four);
EXPECT_EQ(pow(minus_two, three), minus_eight);
EXPECT_EQ(pow(minus_three, two), nine);
EXPECT_EQ(pow(minus_three, three), minus_twenty_seven);
EXPECT_EQ(pow(three, four), eighty_one);
}