| |||||||||||||||||||||||||||||||
| |||||||||||||||||||||||||||||||
| |||||||||||||||||||||||||||||||
| Description | |||||||||||||||||||||||||||||||
RECOMMENDATION: Use Data.Generics.Uniplate.Operations instead. This is the main Uniplate module, which defines all the essential operations in a Haskell 98 compatible manner. Most functions have an example of a possible use for the function. To illustate, I have used the Expr type as below: data Expr = Val Int
| Neg Expr
| Add Expr Expr
| |||||||||||||||||||||||||||||||
| Synopsis | |||||||||||||||||||||||||||||||
| |||||||||||||||||||||||||||||||
| The Class | |||||||||||||||||||||||||||||||
| type UniplateType on = on -> (Str on, Str on -> on) | |||||||||||||||||||||||||||||||
The type of replacing all the children of a node Taking a value, the function should return all the immediate children of the same type, and a function to replace them. | |||||||||||||||||||||||||||||||
| class Uniplate on where | |||||||||||||||||||||||||||||||
| |||||||||||||||||||||||||||||||
| uniplateList :: Uniplate on => on -> ([on], [on] -> on) | |||||||||||||||||||||||||||||||
| Compatibility method, for direct users of the old list-based uniplate function | |||||||||||||||||||||||||||||||
| The Operations | |||||||||||||||||||||||||||||||
| Queries | |||||||||||||||||||||||||||||||
| universe :: Uniplate on => on -> [on] | |||||||||||||||||||||||||||||||
Get all the children of a node, including itself and all children. universe (Add (Val 1) (Neg (Val 2))) =
[Add (Val 1) (Neg (Val 2)), Val 1, Neg (Val 2), Val 2]
This method is often combined with a list comprehension, for example: vals x = [i | Val i <- universe x] | |||||||||||||||||||||||||||||||
| children :: Uniplate on => on -> [on] | |||||||||||||||||||||||||||||||
Get the direct children of a node. Usually using universe is more appropriate. children = fst . uniplate | |||||||||||||||||||||||||||||||
| Transformations | |||||||||||||||||||||||||||||||
| transform :: Uniplate on => (on -> on) -> on -> on | |||||||||||||||||||||||||||||||
Transform every element in the tree, in a bottom-up manner. For example, replacing negative literals with literals: negLits = transform f
where f (Neg (Lit i)) = Lit (negate i)
f x = x
| |||||||||||||||||||||||||||||||
| transformM :: (Monad m, Uniplate on) => (on -> m on) -> on -> m on | |||||||||||||||||||||||||||||||
| Monadic variant of transform | |||||||||||||||||||||||||||||||
| rewrite :: Uniplate on => (on -> Maybe on) -> on -> on | |||||||||||||||||||||||||||||||
Rewrite by applying a rule everywhere you can. Ensures that the rule cannot be applied anywhere in the result: propRewrite r x = all (isNothing . r) (universe (rewrite r x)) Usually transform is more appropriate, but rewrite can give better compositionality. Given two single transformations f and g, you can construct f mplus g which performs both rewrites until a fixed point. | |||||||||||||||||||||||||||||||
| rewriteM :: (Monad m, Uniplate on) => (on -> m (Maybe on)) -> on -> m on | |||||||||||||||||||||||||||||||
| Monadic variant of rewrite | |||||||||||||||||||||||||||||||
| descend :: Uniplate on => (on -> on) -> on -> on | |||||||||||||||||||||||||||||||
| Perform a transformation on all the immediate children, then combine them back. This operation allows additional information to be passed downwards, and can be used to provide a top-down transformation. | |||||||||||||||||||||||||||||||
| descendM :: (Monad m, Uniplate on) => (on -> m on) -> on -> m on | |||||||||||||||||||||||||||||||
| Monadic variant of descend | |||||||||||||||||||||||||||||||
| Others | |||||||||||||||||||||||||||||||
| contexts :: Uniplate on => on -> [(on, on -> on)] | |||||||||||||||||||||||||||||||
Return all the contexts and holes. propUniverse x = universe x == map fst (contexts x) propId x = all (== x) [b a | (a,b) <- contexts x] | |||||||||||||||||||||||||||||||
| holes :: Uniplate on => on -> [(on, on -> on)] | |||||||||||||||||||||||||||||||
The one depth version of contexts propChildren x = children x == map fst (holes x) propId x = all (== x) [b a | (a,b) <- holes x] | |||||||||||||||||||||||||||||||
| para :: Uniplate on => (on -> [r] -> r) -> on -> r | |||||||||||||||||||||||||||||||
| Perform a fold-like computation on each value, technically a paramorphism | |||||||||||||||||||||||||||||||
| module Data.Generics.Str | |||||||||||||||||||||||||||||||
| Produced by Haddock version 2.7.2 |