big: Add Python implementation of LCM.

core/math/big/private.odin

@@ -1642,8 +1642,8 @@ _private_int_gcd_lcm :: proc(res_gcd, res_lcm, a, b: ^Int, allocator := context.
 		/*
 			Store quotient in `t2` such that `t2 * a` is the LCM.
 		*/
-		internal_div(res_lcm, a, temp_gcd_res) or_return
-		err = internal_mul(res_lcm, res_lcm, b)
+		internal_div(res_lcm, b, temp_gcd_res) or_return
+		err = internal_mul(res_lcm, res_lcm, a)
 	}
 
 	if res_gcd != nil {

core/math/big/tests/test.py

@@ -236,24 +236,40 @@ def arg_to_odin(a):
 	return s.encode('utf-8')
 
 
-def integer_sqrt(src):
-		# The Python version on Github's CI doesn't offer math.isqrt.
-		# We implement our own
-		count = src.bit_length()
-		a, b = count >> 1, count & 1
+def big_integer_sqrt(src):
+	# The Python version on Github's CI doesn't offer math.isqrt.
+	# We implement our own
+	count = src.bit_length()
+	a, b = count >> 1, count & 1
 
-		x = 1 << (a + b)
+	x = 1 << (a + b)
 
-		while True:
-			# y = (x + n // x) // 2
-			t1 = src // x
-			t2 = t1  + x
-			y = t2 >> 1
+	while True:
+		# y = (x + n // x) // 2
+		t1 = src // x
+		t2 = t1  + x
+		y = t2 >> 1
 
-			if y >= x:
-				return x
+		if y >= x:
+			return x
 
-			x, y = y, x
+		x, y = y, x
+
+def big_integer_lcm(a, b):
+	# Computes least common multiple as `|a*b|/gcd(a,b)`
+	# Divide the smallest by the GCD.
+
+	if a == 0 or b == 0:
+		return 0
+
+	if abs(a) < abs(b):
+		# Store quotient in `t2` such that `t2 * b` is the LCM.
+		lcm = a // math.gcd(a, b)
+		return abs(b * lcm)
+	else:
+		# Store quotient in `t2` such that `t2 * a` is the LCM.
+		lcm = b // math.gcd(a, b)
+		return abs(a * lcm)
 
 def test_add(a = 0, b = 0, expected_error = Error.Okay):
 	args = [arg_to_odin(a), arg_to_odin(b)]
@@ -358,7 +374,7 @@ def test_sqrt(number = 0, expected_error = Error.Okay):
 		if number < 0:
 			expected_result = 0
 		else:
-			expected_result = integer_sqrt(number)
+			expected_result = big_integer_sqrt(number)
 	return test("test_sqrt", res, [number], expected_error, expected_result)
 
 def root_n(number, root):
@@ -461,7 +477,7 @@ def test_lcm(a = 0, b = 0, expected_error = Error.Okay):
 	res   = int_lcm(*args)
 	expected_result = None
 	if expected_error == Error.Okay:
-		expected_result = math.lcm(a, b)
+		expected_result = big_integer_lcm(a, b)
 		
 	return test("test_lcm", res, [a, b], expected_error, expected_result)
 
@@ -470,7 +486,7 @@ def test_is_square(a = 0, b = 0, expected_error = Error.Okay):
 	res   = is_square(*args)
 	expected_result = None
 	if expected_error == Error.Okay:
-		expected_result = str(integer_sqrt(a) ** 2 == a) if a > 0 else "False"
+		expected_result = str(big_integer_sqrt(a) ** 2 == a) if a > 0 else "False"
 		
 	return test("test_is_square", res, [a], expected_error, expected_result)
 
@@ -703,6 +719,15 @@ if __name__ == '__main__':
 					b = randint(0, min(BITS, 120))
 				elif test_proc == test_is_square:
 					a = randint(0, 1 << BITS)
+				elif test_proc == test_lcm:
+					smallest = min(a, b)
+					biggest  = max(a, b)
+
+					# Randomly swap biggest and smallest
+					if randint(1, 11) % 2 == 0:
+						smallest, biggest = biggest, smallest
+
+					a, b = smallest, biggest
 				else:
 					b = randint(0, 1 << BITS)