Returns a triangle's surface area from the length of its 3 sides, in a numerically stable fashion

triangle-surface-area.py

'''
Compute a triangle's area from its edges length with Heron's formula
Numerically stable
'''
def triangle_area_from_lengths(a, b, c):
	# Sort input
	c, b, a = sorted((a, b, c))

	# Compute Heron's formula
	ret = (a + (b + c)) * (c - (a - b)) * (c + (a - b)) * (a + (b - c))
	return .25 * ret ** .5