robrix / interval-functor

General purpose intervals of functors.

interval-functor

This is a Haskell package defining an Interval datatype parameterized by the type of endpoints and the type of their coordinates. For example, it can represent a simple one-dimensional range:

import Data.Functor.Identity
import Data.Functor.Interval

zeroInterval :: Num a => Interval Identity a
zeroInterval = point 0

or a multi-dimensional region:

import Data.Functor.Interval
import Linear.V3 -- from the linear package

unitCube :: Num a => Interval V3 a
unitCube = (-1)...1

Development

Development currently assumes a Mac with ghc 8.10 & cabal 3.0. You can install them directly, or use ghcup. It should be possible to develop on other platforms and compilers, but I probably haven’t tried them myself.

cabal build --enable-tests # initial build
script/repl # load the library and tests in ghci

Once the repl has loaded, you can run the tests with :main.

λ :main

Configuration exists for ghcide, which can be integrated into many editors.

Advantages

interval-functor separates the representation of the coordinates of an interval from the representation of the space the coordinates occur in. This makes it particularly suitable for consistent treatment of multi-dimensional intervals; operations like e.g. union extend naturally to multi-dimensional spaces.

It is also thoroughly property tested and documented.