|
|
|
|
|
Description |
RECOMMENDATION Use Data.Generics.UniplateStr 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 -> ([on], [on] -> on) | Source |
|
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.
|
|
|
The standard Uniplate class, all operations require this
| | Methods | | The underlying method in the class
uniplate (Add (Val 1) (Neg (Val 2))) = ([Val 1, Neg (Val 2)], \[a,b] -> Add a b)
uniplate (Val 1) = ([] , \[] -> Val 1 )
|
|
|
|
The Operations
|
|
Queries
|
|
|
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]
|
|
|
Get the direct children of a node. Usually using universe is more appropriate.
children = fst . uniplate |
|
Transformations
|
|
|
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
|
|
|
Monadic variant of transform
|
|
|
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.
|
|
|
Monadic variant of rewrite
|
|
|
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.
|
|
|
Monadic variant of descend
|
|
Others
|
|
|
Return all the contexts and holes.
propUniverse x = universe x == map fst (contexts x)
propId x = all (== x) [b a | (a,b) <- contexts x]
|
|
|
The one depth version of contexts
propChildren x = children x == map fst (holes x)
propId x = all (== x) [b a | (a,b) <- holes x]
|
|
|
Perform a fold-like computation on each value,
technically a paramorphism
|
|
Produced by Haddock version 2.4.2 |