# Mapping a function on a stream

Define the functional with the following type
LMap: forall (A B:Set), (A ->B) -> LList A -> LList B

such that `LMap f u` is the list of images by `f` of
all elements of `u`.

Can you define the functional with the following type
LMapcan: forall (A B:Set), (A -> LList B) -> LList A -> LList B

such that `LMapcan f u` is the concatenation by `LAppend`
of the images by `f` of
all elements of `u` ?
## Solution

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Pierre Castéran