Difference between revisions of "TypeCompose"
(corrected darcs repo pointer.) |
m |
||
| (4 intermediate revisions by 4 users not shown) | |||
| Line 1: | Line 1: | ||
| − | [[Category: |
+ | [[Category:Applicative Functor]] |
| − | [[Category:Applicative]] |
||
[[Category:Libraries]] |
[[Category:Libraries]] |
||
[[Category:Packages]] |
[[Category:Packages]] |
||
| Line 12: | Line 11: | ||
* Visit the [http://hackage.haskell.org/cgi-bin/hackage-scripts/package/TypeCompose Hackage page] for library documentation and to download & install. |
* Visit the [http://hackage.haskell.org/cgi-bin/hackage-scripts/package/TypeCompose Hackage page] for library documentation and to download & install. |
||
* Or install with <tt>cabal install TypeCompose</tt>. |
* Or install with <tt>cabal install TypeCompose</tt>. |
||
| − | * Get the code repository: <tt> |
+ | * Get the code repository: <tt>git clone git@github.com:conal/TypeCompose.git</tt>. |
<!--* See the [[TypeCompose/Versions| version history]].--> |
<!--* See the [[TypeCompose/Versions| version history]].--> |
||
| Line 40: | Line 39: | ||
=== References === |
=== References === |
||
| − | Monads with references. Direct rip-off from [http:// |
+ | Monads with references. Direct rip-off from [http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.23.145 Global Variables in Haskell]. |
=== Titling === |
=== Titling === |
||
Latest revision as of 22:44, 29 June 2021
Abstract
TypeCompose provides some classes & instances for forms of type composition, as well as some modules that haven't found another home.
Besides this wiki page, here are more ways to find out about TypeCompose:
- Visit the Hackage page for library documentation and to download & install.
- Or install with cabal install TypeCompose.
- Get the code repository: git clone git@github.com:conal/TypeCompose.git.
Type composition
The Control.Compose module includes
- Various type compositions (unary/unary, binary/unary, etc). Most are from Applicative Programming with Effects. In particular,
g `O` fcomposes functors in to functors and applicative functors (AFs) into AFs. (In contrast, monads do not in general compose.) Composition makes AF-based programming simple and elegant, partly because we don't need an AF counterpart to monad transformers. - Cofunctors (contravariant functors). Great for "consumer" types, just as functors suit "producer" (container) types. There are several composition options.
- Type argument flip. Handy for cofunctors: use
Flip (->) o, for(-> o). - Constructor in pairs:
(f a, g a). - Constructor in arrows/functions:
f a ~> g a.
Other features
Composable bijections
Given all the type constructors and compositions of them, I found myself writing some pretty awkward code to wrap & unwrap through multiple layers. Composable bijections help a lot.
The Data.Bijection module is inspired by There and Back Again: Arrows for Invertible Programming, though done here in a less general setting.
Pair- & function-like types
The Data.Zip and Data.Lambda patterns emerged while working on DeepArrow and Eros. Data.Zip generalizes zip and unzip from [] to other functors. It also provides variants of type f a -> f (a,b) and f a -> f (a,b). Data.Lambda is similar with classes for lambda-like constructions.
For example uses of Pair and Lambda, see TV and Eros.
References
Monads with references. Direct rip-off from Global Variables in Haskell.
Titling
For giving titles to things. I know it sounds kind of random. More useful than I first thought. Used in Phooey, TV, and Eros.
Partial values
A monoid of partial values. See the teaser and solution blog posts.
Context-dependent monoids
Bit of an oddball also. Data.CxMonoid defines a sort of meta-monoid, that can be supplied dynamically with choices of mempty and mappend. Used in Phooey (starting with version 1.3) so that layout could be a monoid but still vary in style.