semi-iso-1.0.0.0: semi-iso.cabal
name: semi-iso
version: 1.0.0.0
synopsis: Weakened partial isomorphisms, reversible computations.
description:
Semi-isomorphisms are partial isomorphisms with weakened iso laws. They are a basic
building block of reversible computations. And they work with Iso and Prism from @lens@!
.
The module "Control.Lens.SemiIso" defines semi-isomorphisms and provides some
basic semi-isos and combinators. A @SemiIso' a b@ can be applied in both directions
to get a @a -> Either String b@ and @b -> Either String a@. SemiIsos can be composed
with Isos and Prisms (to get another SemiIso). Isos and Prisms can be directly
used as SemiIsos.
.
Semi-isomorphisms obey weaker laws then isomorphisms. We require only
.
> apply f >=> unapply f >=> apply f = apply f
> unapply f >=> apply f >=> unapply f = unapply f
.
instead of
.
> apply f >=> unapply f = f
> unapply f >=> apply f = f
.
Modules "Control.SIArrow" and "Control.Category.Structures" define an @Arrow@-like class
hierarchy. Unfortunately "Control.Arrow" cannot be used, as it is too restrictive (the
dreaded @arr@).
SIArrow abstracts categories of reversible computations (with reversible side effects). In
the case of parsing and pretty-printing using the "syntax" library if we have an arrow
@SIArrow cat => cat a b@ then we can:
.
* Evaluate it from left to right, turning a value of type @a@ into a value of type @b@,
with the side effect of consuming a sequence. (Parsing)
.
* Evaluate it from right to left, turning a value of type @b@ into a value of type @a@,
with the side effect of generating a sequence. (Pretty-printing)
.
In the particular case of parsing/pretty-printing the type @a@ will be usually @()@, e.g.
we just produce a value during parsing and just consume a value during pretty-printing.
To support this style we define a functor and applicative structure on @cat () b@, for example
'/*/' (equivalent of '<*>') has type @(\/*\/) :: SIArrow cat => cat () a -> cat () b -> cat () (a, b)@.
.
When more power then applicative is needed - for example when the syntax depends on the
parsed value - we turn back to arrow composition.
.
Module "Control.Category.Reader" defines a Reader category transformer. It is like a monad
transformer, but for categories. The next version will include some more transformers and
mtl-style classes.
license: MIT
license-file: LICENSE
author: Paweł Nowak
maintainer: Paweł Nowak <pawel834@gmail.com>
copyright: Paweł Nowak 2014
category: Control, Data
build-type: Simple
cabal-version: >=1.10
source-repository head
type: git
location: git@github.com:Pawel834/semi-iso.git
library
exposed-modules: Control.Lens.SemiIso
Control.Lens.Internal.SemiIso
Control.SIArrow
Control.Category.Reader
Control.Category.Structures
Data.Profunctor.Exposed
build-depends: base >= 4 && < 5, profunctors, transformers, lens, tuple-morph, semigroupoids
default-language: Haskell2010
ghc-options: -Wall