{-# LANGUAGE FlexibleContexts #-} {-# LANGUAGE MultiParamTypeClasses #-} {-# LANGUAGE TypeFamilies #-} {-# LANGUAGE TypeSynonymInstances #-} ----------------------------------------------------------------------------- -- | -- Module : Diagrams.TwoD.Ellipse -- Copyright : (c) 2011 diagrams-lib team (see LICENSE) -- License : BSD-style (see LICENSE) -- Maintainer : diagrams-discuss@googlegroups.com -- -- Two-dimensional ellipses (and, as a special case, circles). -- ----------------------------------------------------------------------------- module Diagrams.TwoD.Ellipse ( -- * Ellipse and circle diagrams unitCircle , circle , ellipse , ellipseXY ) where import Diagrams.Core import Diagrams.Angle import Diagrams.Located (at) import Diagrams.Trail (glueTrail) import Diagrams.TrailLike import Diagrams.TwoD.Arc import Diagrams.TwoD.Transform import Diagrams.TwoD.Types import Diagrams.TwoD.Vector (xDir) import Diagrams.Util -- | A circle of radius 1, with center at the origin. unitCircle :: (TrailLike t, V t ~ V2, N t ~ n, RealFloat n) => t unitCircle = trailLike \$ glueTrail (arcT xDir fullTurn) `at` p2 (1,0) -- | A circle of the given radius, centered at the origin. As a path, -- it begins at (r,0). circle :: (TrailLike t, V t ~ V2, N t ~ n, RealFloat n, Transformable t) => n -> t circle d = unitCircle # scale d -- | @ellipse e@ constructs an ellipse with eccentricity @e@ by -- scaling the unit circle in the X direction. The eccentricity must -- be within the interval [0,1). ellipse :: (TrailLike t, V t ~ V2, N t ~ n, RealFloat n, Transformable t) => n -> t ellipse e | e >= 0 && e < 1 = scaleX (sqrt (1 - e*e)) unitCircle | otherwise = error "Eccentricity of ellipse must be >= 0 and < 1." -- | @ellipseXY x y@ creates an axis-aligned ellipse, centered at the -- origin, with radius @x@ along the x-axis and radius @y@ along the -- y-axis. ellipseXY :: (TrailLike t, V t ~ V2, N t ~ n, RealFloat n, Transformable t) => n -> n -> t ellipseXY x y = unitCircle # scaleX x # scaleY y