[Haskell-cafe] How to handle recoverable errors in multi-step computation?

[Nickolay Kudasov]

You might also want to check out Chronicle monad in these package:
https://hackage.haskell.org/package/these-0.6.2.1/docs/Control-Monad-Chronicle.html

Kind regards,
Nick
On Sat, 6 Feb 2016 at 11:58, Roman Cheplyaka <roma at ro-che.info> wrote:

> It sounds like you want the Validation applicative functor.
> See e.g. https://ro-che.info/articles/2015-05-02-smarter-validation
>
> On 02/06/2016 04:58 AM, Lian Hung Hon wrote:
> > Dear haskellers,
> >
> > I have a multi-step computation. The steps are predefined, but users can
> > choose which steps to execute (something like a recipe). Here is an
> > example recipe:
> >
> > Step 1 - Get data from network (multiple HTTP calls) and put into a list
> > Step 2 - Process the data (e.g. average, sum, median, etc.)
> > Step 3 - Persist result to database
> >
> > Sometimes, Step 1 can fail for some of the HTTP calls. When this
> > happens, Step 2 should continue as much as possible using whatever data
> > that has been retrieved, but somehow indicate that an error has occurred
> > and the result is partial.
> >
> > Q1: What is the idiomatic way of achieving this? Using throwError in
> > Control.Monad.Except aborts the computation, which isn't what I want.
> >
> > Q2: (General software design) Furthermore, where should the error be
> > logged? Logging it in both Step 1 and 2 preserves modularity for each of
> > the steps, unfortunately it would result in duplicate error messages.
> > What is the best practice for this?
> >
> > Regards,
> > Hon
> >
> >
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> >
>
>
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