mapM_ for bytestring

Shachaf Ben-Kiki shachaf at
Sun Sep 1 18:31:54 CEST 2013

On Sun, Sep 1, 2013 at 3:58 AM, Artyom Kazak <yom at> wrote:
> Would this be an appropriate place to propose adding mapM_ (and then
> possibly mapM) to bytestring library?
> Was it suggested before? If yes, why was it rejected?

For what it's worth, this is exported by lens in
Data.ByteString.Lens.bytes (or
Data.ByteString.{Lazy,Strict}.Lens.bytes). The version exported by
lens by default traverses each chunk in a balanced tree shape rather
than left-to-right (which is probably not relevant to most use cases,
actually -- the result is the same). It also works around
<>, which you'll want to
watch for if you're writing this yourself. Note that you can construct
mapM_ from mapM as discussed in another libraries@ thread recently (or
by using e.g. mapMOf_).


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