{-# LANGUAGE BangPatterns #-}
-- |
-- == Point and vector arithmetic
--
-- Vectors aren't numbers according to Haskell, because they don't
-- support all numeric operations sensibly. We define component-wise
-- addition, subtraction, and negation along with scalar multiplication
-- in this module, which is intended to be imported qualified.
module Graphics.Gloss.Data.Point.Arithmetic
(
Point
, (+)
, (-)
, (*)
, negate
) where
import Prelude (Float)
import qualified Prelude as P
import Graphics.Gloss.Rendering (Point)
infixl 6 +, -
infixl 7 *
-- | Add two vectors, or add a vector to a point.
(+) :: Point -> Point -> Point
(x1, y1) + (x2, y2) =
let
!x = x1 P.+ x2
!y = y1 P.+ y2
in (x, y)
-- | Subtract two vectors, or subtract a vector from a point.
(-) :: Point -> Point -> Point
(x1, y1) - (x2, y2) =
let
!x = x1 P.- x2
!y = y1 P.- y2
in (x, y)
-- | Negate a vector.
negate :: Point -> Point
negate (x, y) =
let
!x' = P.negate x
!y' = P.negate y
in (x', y')
-- | Multiply a scalar by a vector.
(*) :: Float -> Point -> Point
(*) s (x, y) =
let
!x' = s P.* x
!y' = s P.* y
in (x', y')