traverse -package:backprop

Map each element of a structure to an action, evaluate these actions from left to right, and collect the results. For a version that ignores the results see traverse_.

Examples

Basic usage: In the first two examples we show each evaluated action mapping to the output structure.

>>> traverse Just [1,2,3,4]
Just [1,2,3,4]

>>> traverse id [Right 1, Right 2, Right 3, Right 4]
Right [1,2,3,4]

In the next examples, we show that Nothing and Left values short circuit the created structure.

>>> traverse (const Nothing) [1,2,3,4]
Nothing

>>> traverse (\x -> if odd x then Just x else Nothing)  [1,2,3,4]
Nothing

>>> traverse id [Right 1, Right 2, Right 3, Right 4, Left 0]
Left 0

Perform an Applicative action for each key-value pair in a KeyMap and produce a KeyMap of all the results.

Transform the original string-like value but keep it case insensitive.

Deprecated: Use traverse_ instead

Deprecated: Use traverse_ instead

Unstructured traversal.

Foldable instance would allow to strip off the exception too easily. I like the methods of Traversable, but Traversable instance requires Foldable instance.

A transformation, which traverses the stream with an action in the inner monad.

Map each element of a structure to an action, evaluate these actions from left to right, and collect the results. For a version that ignores the results see traverse_.

Map each element of the array to an action, evaluate these actions from left to right, and collect the results. For a version that ignores the results, see traverse_.

Traverse a function over a record. Note that the fields of the record will be accessed in lexicographic order by the labels.

Traverse a function over a variant.

O(n log n). Traverse the elements of the heap in sorted order and produce a new heap using Applicative side-effects.

Map each element of a structure to an action, evaluate these actions from left to right, and collect the results. For a version that ignores the results see traverse_.

Analog of traverse from Traversable.

Traverse a sorted list with a function that returns in a monad. The same performance observations apply here as in map, as changing the values may involve reordering the list.

Apply an action to every element of a Vec, yielding a Vec of results.

Apply an action to every element of a Vec, yielding a Vec of results.

A more general implementation of traverse, because it can also work to, from, or within monomorphic structures, obviating the need for classes like MonoTraversable.