Safe Haskell | None |
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All of the functions below work only on «interesting» subterms It is up to the instance writer to decide which subterms are
interesting and which subterms should count as immediate. This can
also depend on the context `c`

.

The context, denoted `c`

, is a constraint (of kind `* -> Constraint`

)
that provides additional facilities to work with the data. Most
functions take an implicit parameter `?c :: p c`

; it's
used to disambugate which context you are referring to. `p`

can be
`Proxy`

from the `tagged`

package or any other suitable type
constructor.

For more information, see:

- Scrap your boilerplate with class
- http://research.microsoft.com/en-us/um/people/simonpj/papers/hmap/
- Generalizing generic fold
- http://ro-che.info/articles/2013-03-11-generalizing-gfoldl.html

- class GTraversable c a where
- gtraverse :: (Applicative f, [c :: p c]) => (forall d. c d => d -> f d) -> a -> f a

- gmap :: (GTraversable c a, [c :: p c]) => (forall d. c d => d -> d) -> a -> a
- gmapM :: (Monad m, GTraversable c a, [c :: p c]) => (forall d. c d => d -> m d) -> a -> m a
- gfoldMap :: (Monoid r, GTraversable c a, [c :: p c]) => (forall d. c d => d -> r) -> a -> r
- gfoldr :: (GTraversable c a, [c :: p c]) => (forall d. c d => d -> r -> r) -> r -> a -> r
- gfoldl' :: (GTraversable c a, [c :: p c]) => (forall d. c d => r -> d -> r) -> r -> a -> r
- class (GTraversable (Rec c) a, c a) => Rec c a
- everywhere :: forall a c p. (Rec c a, [c :: p c]) => (forall d. Rec c d => d -> d) -> a -> a
- everywhere' :: forall a c p. (Rec c a, [c :: p c]) => (forall d. Rec c d => d -> d) -> a -> a
- everywhereM :: forall m a c p. (Monad m, Rec c a, [c :: p c]) => (forall d. Rec c d => d -> m d) -> a -> m a
- everything :: forall r a c p. (Rec c a, [c :: p c]) => (r -> r -> r) -> (forall d. Rec c d => d -> r) -> a -> r

# Open recursion combinators

class GTraversable c a whereSource

gtraverse :: (Applicative f, [c :: p c]) => (forall d. c d => d -> f d) -> a -> f aSource

Applicative traversal over (a subset of) immediate subterms. This is
a generic version of `traverse`

from Data.Traversable.

The supplied function is applied only to the «interesting» subterms

Other subterms are lifted using `pure`

, and the whole structure is
folded back using `<*>`

.

`gtraverse`

has a default implementation `const pure`

, which works for
types without interesting subterms (in particular, atomic types).

GTraversable c Ordering | |

GTraversable c Char | |

GTraversable c Double | |

GTraversable c Float | |

GTraversable c Integer | |

GTraversable c Int | |

GTraversable c Bool | |

GTraversable c () | |

GTraversable c (Ratio n) | |

c0 a0 => GTraversable c0 (Maybe a0) | |

c a => GTraversable c [a] | |

(c0 a0, c0 b0) => GTraversable c0 (Either a0 b0) | |

(c0 a0, c0 b0) => GTraversable c0 (a0, b0) | |

(c0 a0, c0 b0, c0 c1) => GTraversable c0 (a0, b0, c1) |

gmap :: (GTraversable c a, [c :: p c]) => (forall d. c d => d -> d) -> a -> aSource

Generic map over the immediate subterms

gmapM :: (Monad m, GTraversable c a, [c :: p c]) => (forall d. c d => d -> m d) -> a -> m aSource

Generic monadic map over the immediate subterms

gfoldMap :: (Monoid r, GTraversable c a, [c :: p c]) => (forall d. c d => d -> r) -> a -> rSource

Generic monoidal fold over the immediate subterms (cf. `foldMap`

from
Data.Foldable)

gfoldr :: (GTraversable c a, [c :: p c]) => (forall d. c d => d -> r -> r) -> r -> a -> rSource

Generic right fold over the immediate subterms

gfoldl' :: (GTraversable c a, [c :: p c]) => (forall d. c d => r -> d -> r) -> r -> a -> rSource

Generic strict left fold over the immediate subterms

# Closed recursion combinators

class (GTraversable (Rec c) a, c a) => Rec c a Source

`Rec`

enables "deep traversals".

It is satisfied automatically when its superclass constraints are satisfied — you are not supposed to declare new instances of this class.

(GTraversable (Rec c) a, c a) => Rec c a |

everywhere :: forall a c p. (Rec c a, [c :: p c]) => (forall d. Rec c d => d -> d) -> a -> aSource

Apply a transformation everywhere in bottom-up manner

everywhere' :: forall a c p. (Rec c a, [c :: p c]) => (forall d. Rec c d => d -> d) -> a -> aSource

Apply a transformation everywhere in top-down manner

everywhereM :: forall m a c p. (Monad m, Rec c a, [c :: p c]) => (forall d. Rec c d => d -> m d) -> a -> m aSource

Monadic variation on everywhere

everything :: forall r a c p. (Rec c a, [c :: p c]) => (r -> r -> r) -> (forall d. Rec c d => d -> r) -> a -> rSource

Strict left fold over all elements, top-down