math: gcd and lcm functions

vlib/math/math.v

@@ -68,6 +68,36 @@ pub fn fmod(a, b f64) f64 {
 	return C.fmod(a, b)
 }
 
+// gcd calculates greatest common (positive) divisor (or zero if x and y are both zero).
+pub fn gcd(a, b int) int {
+	if a < 0 {
+		a = -a
+	}
+	if b < 0 {
+		b = -b
+	}
+	for b != 0 {
+		a %= b
+		if a == 0 {
+			return b
+		}
+		b %= a
+	}
+	return a
+}
+
+// lcm calculates least common (non-negative) multiple.
+pub fn lcm(a, b int) int {
+	if a == 0 {
+		return a
+	}
+	res := a * (b / gcd(b, a))
+	if res < 0 {
+		return -res
+	}
+	return res
+}
+
 pub fn log(a f64) f64 {
 	return C.log(a)
 }

vlib/math/math_test.v

@@ -0,0 +1,9 @@
+import math
+
+fn test_gcd_and_lcm() {
+	assert math.gcd(6, 9) == 3
+	assert math.gcd(6, -9) == 3
+
+	assert math.lcm(2, 3) == 6
+	assert math.lcm(-2, 3) == 6
+}