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gloss/gloss-examples/picture/Clock/Main.hs
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-- A fractal consisting of circles and lines which looks a bit like | |
-- the workings of a clock. | |
module Main where | |
import Graphics.Gloss | |
import Prelude hiding ( lines ) | |
main :: IO () | |
main | |
= animate (InWindow "Clock" (600, 600) (20, 20)) | |
black frame | |
-- Build the fractal, scale it so it fits in the window | |
-- and rotate the whole thing as time moves on. | |
frame :: Float -> Picture | |
frame time | |
= Color white | |
$ Scale 120 120 | |
$ Rotate (time * 2*pi) | |
$ clockFractal 5 time | |
-- The basic fractal consists of three circles offset from the origin | |
-- as follows. | |
-- | |
-- 1 | |
-- | | |
-- . | |
-- / \ | |
-- 2 3 | |
-- | |
-- The direction of rotation switches as n increases. | |
-- Components at higher iterations also spin faster. | |
-- | |
clockFractal :: Int -> Float -> Picture | |
clockFractal 0 _ = Blank | |
clockFractal n s = Pictures [circ1, circ2, circ3, lines] | |
where | |
-- y offset from origin to center of circle 1. | |
a = 1 / sin (2 * pi / 6) | |
-- x offset from origin to center of circles 2 and 3. | |
b = a * cos (2 * pi / 6) | |
nf = fromIntegral n | |
rot = if n `mod` 2 == 0 | |
then 50 * s * (log (1 + nf)) | |
else (-50 * s * (log (1 + nf))) | |
-- each element contains a copy of the (n-1) iteration contained | |
-- within a larger circle, and some text showing the time since | |
-- the animation started. | |
-- | |
circNm1 | |
= Pictures | |
[ circle 1 | |
, Scale (a/2.5) (a/2.5) $ clockFractal (n-1) s | |
, if n > 2 | |
then Color cyan | |
$ Translate (-0.15) 1 | |
$ Scale 0.001 0.001 | |
$ Text (show s) | |
else Blank | |
] | |
circ1 = Translate 0 a $ Rotate rot circNm1 | |
circ2 = Translate 1 (-b) $ Rotate (-rot) circNm1 | |
circ3 = Translate (-1) (-b) $ Rotate rot circNm1 | |
-- join each iteration to the origin with some lines. | |
lines | |
= Pictures | |
[ Line [(0, 0), ( 0, a)] | |
, Line [(0, 0), ( 1, -b)] | |
, Line [(0, 0), (-1, -b)] ] |