[Haskell-beginners] How to structure a "speaking" fuzzy clock?
daniel.is.fischer at googlemail.com
Sun Jan 16 16:14:04 CET 2011
On Sunday 16 January 2011 15:16:46, Kamil Stachowski wrote:
> 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
= 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
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
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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