Improved quadratic function solver; added wrapper for math.sqrt()

1 files changed, 10 insertions, 1 deletions

diff --git a/advtrains/helpers.lua b/advtrains/helpers.lua
index a2eabb5..9afe72d 100644
--- a/advtrains/helpers.lua
+++ b/advtrains/helpers.lua
@@ -398,13 +398,22 @@ function advtrains.decode_pos(pts)
 	return vector.new(dec(strx), dec(stry), dec(strz))

 end

 

+-- Solve quadratic equations (i.e. a*x^2 + b*x + c = 0)

 function advtrains.solve_quadratic_equation(a, b, c)

 	if not (a and b and c) then return nil end

+	if a == 0 then return {-c/b, -c/b} end -- avoid division by zero

 	local delta = (b*b - 4*a*c)

-	if delta < 0 then return nil end

+	if delta < 0 then return {-b/2/a,-b/2/a} end -- ignore imaginary part

 	return {((-b+math.sqrt(delta))/2/a),((-b-math.sqrt(delta))/2/a)}

 end

 

+-- safe square root

+-- Negative return values indicate imaginary numbers.

+function advtrains.safesqrt(a)

+	if a >= 0 then return math.sqrt(a) end

+	return 0 - math.sqrt(-a)

+end

+

 --[[ Benchmarking code

 local tdt = {}

 local tlt = {}