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// Copyright © 2021 siddharth ravikumar <s@ricketyspace.net>
// SPDX-License-Identifier: ISC
package lib
import (
"math/big"
"testing"
)
func TestEGCD(t *testing.T) {
a := big.NewInt(128)
b := big.NewInt(96)
r := egcd(a, b)
if r.Gcd.Cmp(big.NewInt(32)) != 0 {
t.Errorf("gcd(128, 96) != 32")
}
if r.X.Cmp(big.NewInt(1)) != 0 || r.Y.Cmp(big.NewInt(-1)) != 0 {
t.Errorf("bézout_coef(128, 96) != {1,-1}")
}
a = big.NewInt(360)
b = big.NewInt(210)
r = egcd(a, b)
if r.Gcd.Cmp(big.NewInt(30)) != 0 {
t.Errorf("gcd(360, 210) != 30")
}
if r.X.Cmp(big.NewInt(3)) != 0 || r.Y.Cmp(big.NewInt(-5)) != 0 {
t.Errorf("bézout_coef(360, 210) != {3,-5}")
}
a = big.NewInt(108)
b = big.NewInt(144)
r = egcd(a, b)
if r.Gcd.Cmp(big.NewInt(36)) != 0 {
t.Errorf("gcd(108, 144) != 36")
}
if r.X.Cmp(big.NewInt(-1)) != 0 || r.Y.Cmp(big.NewInt(1)) != 0 {
t.Errorf("bézout_coef(108, 144) != {-1,1}")
}
a = big.NewInt(240)
b = big.NewInt(46)
r = egcd(a, b)
if r.Gcd.Cmp(big.NewInt(2)) != 0 {
t.Errorf("gcd(240, 46) != 2")
}
if r.X.Cmp(big.NewInt(-9)) != 0 || r.Y.Cmp(big.NewInt(47)) != 0 {
t.Errorf("bézout_coef(240, 46) != {-9,47}")
}
}
func TestInvMod(t *testing.T) {
a := big.NewInt(17)
b := big.NewInt(3120)
e := big.NewInt(2753) // Expected inverse.
i, err := invmod(a, b)
if err != nil {
t.Errorf("invmod(%v,%v) failed: %v", a, b, err)
}
if i.Cmp(e) != 0 {
t.Errorf("gcd(%v,%v) != %v", a, b, e)
}
a = big.NewInt(240)
b = big.NewInt(47)
e = big.NewInt(19) // Expected inverse.
i, err = invmod(a, b)
if err != nil {
t.Errorf("invmod(%v,%v) failed: %v", a, b, err)
}
if i.Cmp(e) != 0 {
t.Errorf("gcd(%v,%v) != %v", a, b, e)
}
}
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