Initial project import

tools/v/vlib/math/div.v

@@ -0,0 +1,87 @@
+module math
+
+// Floating-point mod function.
+// mod returns the floating-point remainder of x/y.
+// The magnitude of the result is less than y and its
+// sign agrees with that of x.
+//
+// special cases are:
+// mod(±inf, y) = nan
+// mod(nan, y) = nan
+// mod(x, 0) = nan
+// mod(x, ±inf) = x
+// mod(x, nan) = nan
+pub fn mod(x f64, y f64) f64 {
+	return fmod(x, y)
+}
+
+// fmod returns the floating-point remainder of number / denom (rounded towards zero)
+pub fn fmod(x f64, y f64) f64 {
+	if y == 0 || is_inf(x, 0) || is_nan(x) || is_nan(y) {
+		return nan()
+	}
+	abs_y := abs(y)
+	abs_y_fr, abs_y_exp := frexp(abs_y)
+	mut r := x
+	if x < 0 {
+		r = -x
+	}
+	for r >= abs_y {
+		rfr, mut rexp := frexp(r)
+		if rfr < abs_y_fr {
+			rexp = rexp - 1
+		}
+		r = r - ldexp(abs_y, rexp - abs_y_exp)
+	}
+	if x < 0 {
+		r = -r
+	}
+	return r
+}
+
+// gcd calculates greatest common (positive) divisor (or zero if a and b are both zero).
+pub fn gcd(a_ i64, b_ i64) i64 {
+	mut a := a_
+	mut b := b_
+	if a < 0 {
+		a = -a
+	}
+	if b < 0 {
+		b = -b
+	}
+	for b != 0 {
+		a %= b
+		if a == 0 {
+			return b
+		}
+		b %= a
+	}
+	return a
+}
+
+// egcd returns (gcd(a, b), x, y) such that |a*x + b*y| = gcd(a, b)
+pub fn egcd(a i64, b i64) (i64, i64, i64) {
+	mut old_r, mut r := a, b
+	mut old_s, mut s := i64(1), i64(0)
+	mut old_t, mut t := i64(0), i64(1)
+
+	for r != 0 {
+		quot := old_r / r
+		old_r, r = r, old_r % r
+		old_s, s = s, old_s - quot * s
+		old_t, t = t, old_t - quot * t
+	}
+	return if old_r < 0 { -old_r } else { old_r }, old_s, old_t
+}
+
+// lcm calculates least common (non-negative) multiple.
+pub fn lcm(a i64, b i64) i64 {
+	if a == 0 {
+		return a
+	}
+	res := a * (b / gcd(b, a))
+	if res < 0 {
+		return -res
+	}
+	return res
+}