Graphics.Chalkboard.Utils

This module contains some general utilties.

Utilties for R.

innerSteps :: Int -> [R]

innerSteps takes n even steps from 0 .. 1, by not actually touching 0 or 1. The first and last step are 1/2 the size of the others, so that repeated innerSteps can be tiled neatly.

outerSteps :: Int -> [R]

outerSteps takes n even steps from 0 .. 1, starting with 0, and ending with 1, returning n+1 elements.

fracPart :: R -> R

Extract the fractional part of an R.

fromPolar :: (R, Radian) -> Point

toPolar :: Point -> (R, Radian)

angleOfLine :: (Point, Point) -> Radian

Pointwise operators.

interpBool :: Bool -> UI

Covert a Bool (mask point) into a unit interval.

sampleUI :: UI -> Bool

sample a UI, giving a point of a mask.

withMask :: a -> Bool -> Maybe a

Use a mask to create a Just value, or Nothing.

withDefault :: a -> Maybe a -> a

With a default if you do not have a Just.

choose :: a -> a -> Bool -> a

choose between two values.

Point Utilties.

insideRegion :: (Point, Point) -> Point -> Bool

is a Point inside a region?

insideCircle :: Point -> R -> Point -> Bool

is a Point inside a circle, where the first two arguments are the center of the circle, and the radius.

distance :: Point -> Point -> R

What is the distance between two points in R2? This is optimised for the normal form distance p1 p2 <= v, which avoids using sqrt.

intervalOnLine :: (Point, Point) -> Point -> R

intervalOnLine find the place on a line (between 0 and 1) that is closest to the given point.

circleOfDots :: Int -> [Point]

circleOfDots generates a set of points between (-1..1,-1..1), inside a circle.