data-function-tacit alternatives and similar packages
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streaming
An optimized general monad transformer for streaming applications, with a simple prelude of functions -
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text-icu
This package provides the Haskell Data.Text.ICU library, for performing complex manipulation of Unicode text. -
WorkOS - The modern identity platform for B2B SaaS
Do you think we are missing an alternative of data-function-tacit or a related project?
README
Data.Function.Tacit
Write functions in tacit (pointless) style using Applicative and De Bruijn index notation.
Examples:
\f x y -> f x == f y = lurryA @N3 ((==) <$> (_1 <*> _2) (_1 <*> _3))-\f g x -> f x (g x) = lurryA @N3 ((_1 <*> _3) <*> (_2 <*> _3))\a b -> b = lurryA @N2 _2
This module is intended to be used with Control.Applicative but
does not export it.
Opposite to De Bruijn indices, this module orders the arguments
from the outside-in, rather than the inside-out (or left-to-right
instead of right-to-left). For example, the conventional
λλλ3 1 (2 1) is instead λλλ1 3 (2 3).
The first argument is z, the second argument z.s, the third
argument z.s.s, and so on. For the first few arguments convenient
names have been defined, such as _1, _2, _3, and so on.
To export a function use lurryA. You must specify the arity of
the function, which is intended to be done with TypeApplications
(new in GHC 8.0). lurryA @(S Z) f says the arity of @f@ is one,
lurryA @(S (S Z)) f says the arity is two, and so on. For
convenience the first few Peano numbers have been given aliases,
such as N1, N2, N3, and so on.
You can write all functions with <*> and <$> from
Applicative — should be able to, yet unproven.
There is a type inference problem with functions where the highest
index does not match the function arity, such as const. To
resolve this ambiguity you must give an explicit signature. For
example: lurryA @N2 (_1 :: (a, (b, c)) -> a).
TODO:
- Construction rules for rewriting functions into this tacit form. More precise than just examples. Would demonstrate that any function can be written in this tacit form.
- An inverse for
lurry,unlurry. Type inference seems difficult. - Inference problem when the highest index does not match the function arity.
NOTES:
- The implementation would be simpler and less prone to inference
problems if GHC had closed classes. Given a type family
F, a corresponding value-level implementation may exist forx -> F x. This implementation can be given by a class and an instance corresponding to each case in the type family. However, if the type family is closed and we only have open classes, we cannot always define corresponding instances which are unambiguous. An example of this correspondence isLurried/Lurry.