[Haskell-cafe] The Good, the Bad and the GUI

[Alberto G. Corona]

Formlets ever had cascade validation:

data Item= Item{ name ::String, quantity, price :: Int}

Item <$>
       <*> inputString `validate` nonEmpty
       <*> inputInt
       <*> inputInt
 `validate` ( \item -> do
      if theUniverseIsSpanding then do
           if name item == "carrots" && price=="10" then
                       fail "we don´t like 10 cent carrots  in an expanding
universe"
           else if.....


2014-08-14 11:41 GMT+02:00 Tom Ellis <
tom-lists-haskell-cafe-2013 at jaguarpaw.co.uk>:

> On Thu, Aug 14, 2014 at 11:28:53AM +0200, Wojtek Narczyński wrote:
> > On 14.08.2014 09:19, Tom Ellis wrote:
> > >On Wed, Aug 13, 2014 at 05:21:28PM -0700, John Lato wrote:
> > >>On Wed, Aug 13, 2014 at 4:21 PM, Tom Ellis
> > >>>     data LineItem = LineItem { name :: Maybe String
> > >>>                              , quantity :: Maybe Quantity
> > >>>                              , price :: Maybe Price }
> > >>Rather than this definition, what about something like:
> > >>
> > >>     data LineItemF f = LineItem
> > >>         { name :: f String
> > >>         , quantity :: f Quantity
> > >>         , price :: f Price }
> > >It seems Wojtek already objected to this approach, though perhaps that
> > >objection could be overcome
> >
> > Hmm, perhaps like this
> >
> > LineItemFi = LineItemFi
> >    { name :: StringFi
> >    , quantity :: QuantityFi
> >    , price :: PriceFi }
> >
> >
> > data LineItemUi f = LineItemUi
> >     { name :: StringUi
> >     , quantity :: QuantityUi
> >     , price :: PriceUi }
>
> You didn't use f there.
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-- 
Alberto.
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