module Geometry where -- | Game time in turns. (Placement in module Geometry is not ideal.) type Time = Int type X = Int type Y = Int type Loc = (Y,X) type Dir = (Y,X) type Area = ((Y,X),(Y,X)) -- | Given two locations, determine the direction in which one should -- move from the first in order to get closer to the second. Does not -- pay attention to obstacles at all. towards :: (Loc,Loc) -> Dir towards ((y0,x0),(y1,x1)) = let dy = y1 - y0 dx = x1 - x0 angle = atan (fromIntegral dy / fromIntegral dx) / (pi / 2) dir | angle <= -0.75 = (-1,0) | angle <= -0.25 = (-1,1) | angle <= 0.25 = (0,1) | angle <= 0.75 = (1,1) | angle <= 1.25 = (1,0) | otherwise = (0,0) in if dx >= 0 then dir else neg dir -- | Get the squared distance between two locations. distance :: (Loc,Loc) -> Int distance ((y0,x0),(y1,x1)) = (y1 - y0)^2 + (x1 - x0)^2 -- | Return whether two locations are adjacent on the map -- (horizontally, vertically or diagonally). Currrently, a -- position is also considered adjacent to itself. adjacent :: Loc -> Loc -> Bool adjacent s t = distance (s,t) <= 2 -- | Return the 8 surrounding locations of a given location. surroundings :: Loc -> [Loc] surroundings l = map (l `shift`) moves diagonal :: Dir -> Bool diagonal (y,x) = y*x /= 0 -- | Move one square in the given direction. shift :: Loc -> Dir -> Loc shift (y0,x0) (y1,x1) = (y0+y1,x0+x1) -- | Invert a direction (vector). neg :: Dir -> Dir neg (y,x) = (-y,-x) -- | Get the vectors of all the moves. moves :: [Dir] moves = [ (x,y) | x <- [-1..1], y <- [-1..1], x /= 0 || y /= 0 ] up, down, left, right :: Dir upleft, upright, downleft, downright :: Dir upleft = up `shift` left upright = up `shift` right downleft = down `shift` left downright = down `shift` right up = (-1,0) down = (1,0) left = (0,-1) right = (0,1) horiz, vert :: [Dir] horiz = [left, right] vert = [up, down]