CK Kashyap wrote:
Hi All,
I am working on a diagraming utility in Haskell. I started with line drawing. I am doing the basic stuff using the y = mx + c formula to draw a line between (x1,y1) and (x2,y2) Hi,
Are you doing this to learn Haskell, learn about drawing lines, or to just get it implemented? If either of the latter two, when drawing a straight line you shouldn't need to do floating point operations such as this:
newY = y1 + round (slope * (fromIntegral (newX - x1)))
Bresenham's algorithm (or similar variants) allows you to draw a line without needing floating point. A Haskell implementation is here: http://rosettacode.org/wiki/Bresenham%27s_line_algorithm#Haskell Although it may not be too understandable! Wikipedia has an explanation of the general algorithm: http://en.wikipedia.org/wiki/Bresenham%27s_line_algorithm As to how to cope with the dy > dx case in your code given the dx > dy case, you could just swap the x and y coords at the start, then swap back the x and y coords of all the output points afterwards. Odd, but effective :-) Thanks, Neil.