[Haskell-cafe] Accumulating and threading output of functions

[Patrick Chilton]

If c is a Monoid, you can use the RWS a c b () type instead and combine
them with sequence_.
On 4 Jun 2016 5:19 pm, "martin" <martin.drautzburg at web.de> wrote:

> Hello all,
>
> I have a number of functions, whose type is something like this:
>
> f:: a -> b -> (b, c)
>
> i.e. it returns a modified b and an additional c.
>
> Now I want to write a combinator, which assembles a list of such functions
> into a single one. This combinator will have
> to thread the bs from one function to the next and accumulate the cs into
> a single c.
>
> While I was able to write this using a fold, I am not happy with it (my
> first attempt had a bad error in it, which is
> always a bad sign).
>
> Are you aware of any idioms, how to do such things on the beaten track?
>
>
>
>
>
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