indexed-list-literals: Type safe indexed list literals

This is an incredibly simple library, which makes writing lists where the length is known at compile time a little bit nicer.

If you write a function with the signature

vector :: ILL input length output => input -> Vector length output

then

v :: Vector 3 Int
v = vector (1,2,3)

x :: Vector 0 Double
x = vector $ ZeroTuple @Double

y :: Vector 1 Double
y = vector (Only 1)

z :: Vector 2 String
z = vector ("Hello", "World")

If want matrix literals you can write a function

matrix :: (ILL row width ty, ILL matrix height row) => matrix -> Matrix width height ty

then

a :: Matrix 0 0 Bool
a = matrix $ ZeroTuple @(ZeroTuple Bool)

b :: Matrix 1 2 String
b = matrix $ Only ("Hello","World")

c :: Matrix 4 5 Double
c = matrix ((1,2,3,0,0)
           ,(4,5,6,0,0)
           ,(7,8,9,0,0)
           ,(0,0,0,0,0))

The full code is in test/Docs.hs

This only supports literals of length up to 20, though that can be easily extended using the code generator in src/Data/IndexedListLiterals.hs

• Data
  • Data.IndexedListLiterals