Simple torus distribution

Simple torus distribution

.

likeso.js

function randr(min, max) {
    return Math.random() * (max - min) + min;
};

function torusDistribPoint(radius, size) {
	var l = randr(size - radius, size + radius);
	var a = randr(0, 2*Math.PI);
	return [l * Math.cos(a), l * Math.sin(a)];
}

Makefile

all: plot

torus: torusdistr.hs
	ghc --make torusdistr.hs

plot: torus
	./torusdistr > data
	gnuplot plot.gpl

plot.gpl

set terminal png size 400,400 enhanced font "Helvetica,6"
set output 'torus.png'
set autoscale
plot "data" using 1:2

torusdistr.hs

{-# LANGUAGE ScopedTypeVariables #-}

import System.Random (randomR, getStdGen, StdGen)
import Control.Monad (mapM_, replicateM)
import Control.Monad.State

torusDist gen n radius size = transform $ zip xs ys
    where (xs, gen') = randoms n (0, 2*pi) gen
          (ys, _) = randoms n (size - radius, size + radius) gen'

transform :: Floating a => [(a, a)] -> [(a, a)]
transform [] = []
transform ((x, y):ts) = (a, b) : transform ts
    where a = y * sin x
          b = y * cos x

randoms n i = runState (replicateM n (state (randomR i)))

main = do gen <- getStdGen
          let points :: [(Double, Double)] = torusDist gen 100 0.1 0.5
          mapM_ print points
            where print (x, y) = put x >> put y >> putStr "\n"
                  put x = putStr (show x) >> putStr " "