{-# OPTIONS -fno-warn-missing-methods -fno-warn-orphans #-} {-# LANGUAGE TypeSynonymInstances, FlexibleInstances #-} module Graphics.Gloss.Data.Point ( Point , pointInBox) where -- | A point on the x-y plane. -- Points can also be treated as `Vector`s, so "Graphics.Gloss.Data.Vector" may also be useful. type Point = (Float, Float) -- | Pretend a point is a number. -- Vectors aren't real numbes according to Haskell, because they don't -- support the multiply and divide field operators. We can pretend they -- are though, and use the (+) and (-) operators as component-wise -- addition and subtraction. -- instance Num Point where (+) (x1, y1) (x2, y2) = (x1 + x2, y1 + y2) (-) (x1, y1) (x2, y2) = (x1 - x2, y1 - y2) negate (x, y) = (negate x, negate y) -- | Test whether a point lies within a rectangular box that is oriented -- on the x-y plane. The points P1-P2 are opposing points of the box, -- but need not be in a particular order. -- -- @ -- P2 +-------+ -- | | -- | + P0 | -- | | -- +-------+ P1 -- @ -- pointInBox :: Point -> Point -> Point -> Bool pointInBox (x0, y0) (x1, y1) (x2, y2) = x0 >= min x1 x2 && x0 <= max x1 x2 && y0 >= min y1 y2 && y0 <= max y1 y2