[Haskell-beginners] How to structure a "speaking" fuzzy clock?

[Kamil Stachowski]

Oh dear, I didn't actually mean to make you read the whole thing! Thank you
the more!

I'm very happy that you don't think the structure is completely wrong. I was
quite worried about it. But if you say it's not too ugly, I will be able to
sleep at night again :)

Thanks a lot for the tips!


On 16 January 2011 16:14, Daniel Fischer
<daniel.is.fischer at googlemail.com>wrote:

> On Sunday 16 January 2011 15:16:46, Kamil Stachowski wrote:
> > Hello,
> >
> > I am writing a program, the main purpose of which is to print fuzzy time
> > in a casual manner, e.g. "ten to eleven" rather than "10:52".
> > Considering my (lack of) programming experience, I got pretty far with
> > it with the help of D. Fischer and B. Yorgey; you can take a look at the
> > results at https://github.com/caminoix/fuzzytime.
> >
> > However, I also have another purpose, and that is to better learn
> > Haskell. I can't help the feeling that my solution might perhaps work,
> > but is nevertheless ugly, naive or just un-Haskell.
>
> From a quick glance: not too ugly.
>
> In checkFTConf, you have a couple of guards
>
>    | not (thing `elem` list)
>
> which would read better using notElem,
>
>    | thing `notElem` list
>
> checkTimeOk isn't good, better
>
> checkTimeOk
>    = case break (== ':') time of
>        (hh, _:mm) -> let h = read hh
>                          m = read mm
>                      in 0 <= h && h < 24 && 0 <= m && m < 60
>        _ -> False
>
> and to further guard against malformed input, you could also test
> - not (null hh || null mm)
> - all isDigit hh && all isDigit mm -- requires import Data,Char
>
> The message for precision out of range should contain '<=' instead of '<'.
>
> Are you sure you mean humane and not human?
>
> In FuzzyTime, maybe it would be better to have the field fzLang be a new
> datatype Lang instead of a String.
>
> In toFuzzyTime, get hour and min(ute) via break (and not per reverse .
> takeWhile (/= ':') . reverse), like in checkTimeOk
>
> >
> > Therefore, I would like to ask you how you would structure such a
> > program.
>
> Hmm, I would need to think about that. What I can say without thinking:
>
> I'd use a new datatype for style and lang, and instead of checking the
> validity of the FuzzyTimeConf before converting to FuzzyTime, I'd write a
> conversion
>
> foo :: FuzzyTimeConf -> Either ErrorMessage FuzzyTime
>
> and do the checks during the conversion to not repeat work.
>
> > I'm not asking for an implementation, just a general idea, such
> > as "a datatype to keep the fuzzy time, deriving Show with a set of
> > separate functions for different languages".
> >
> > Thanks in advance!
>
>
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