[Haskell-cafe] Additional functionality using cabal configure flags

[Sumit Sahrawat, Maths & Computing, IIT (BHU)]

Thanks. That's just what I needed.

As much as I want to avoid it, it seems that I don't have much choice.
I'm building a calculator-ish repl that also allows plotting. I don't want
the users to have to install gtk and all that stuff if they don't require
it.
I'll try and refactor my code to see what I can do, but that would mean
less extensibility.
I started out with the expression problem, and now I might have to work
against what I built.

On 13 March 2015 at 13:05, Konstantine Rybnikov <k-bx at k-bx.com> wrote:

> Sumit,
>
> Here's an example:
>
> ```
> flag production
>   default: False
>
> Executable Foo
>   if flag(production)
>     cpp-options: -DPRODUCTION
> ```
>
> I should note that while I have this mechanism in my code, I think that
> overall it wasn't a good choice, and I'd rather prefer parsing a
> command-line argument and passing it through my code in stead of having a
> flag like this. It makes code much harder to write, because each usage has
> heavy syntax of:
>
> ```
> #ifdef PRODUCTION
> something
> #else
> somethingElse
> #endif
> ```
>
> while instead you could just write:
>
> ```
> if production then something else somethingElse
> ```
>
>
>
> On Thu, Mar 12, 2015 at 11:43 PM, Sumit Sahrawat, Maths & Computing, IIT
> (BHU) <sumit.sahrawat.apm13 at iitbhu.ac.in> wrote:
>
>> Hi Konstantine, thanks for the reply
>>
>> I decide to use flags, but then the trouble is that I will need some
>> mechanism to flag parts of the code, possibly using the CPP extension.
>> I wanted to know whether there is a better way. Also, does CPP allow
>> checking cabal configure flags? The user-guide did not mention such
>> usecases.
>>
>> On 13 March 2015 at 02:23, Konstantine Rybnikov <k-bx at k-bx.com> wrote:
>>
>>> Hi Sumit,
>>>
>>> Documentation clearly mentions it is related to API, so don't worry with
>>> executable and feel free to use the flags (still, depending on what are you
>>> doing, flags might not be the best solution).
>>> 12 бер. 2015 18:40, користувач "Sumit Sahrawat, Maths & Computing, IIT
>>> (BHU)" <sumit.sahrawat.apm13 at iitbhu.ac.in> написав:
>>>
>>>> Hi everybody,
>>>>
>>>> I am looking for the correct way to provide additional functionality
>>>> using cabal configure flags.
>>>> Even though the developer faq [1] says that it is not recommended, I
>>>> don't see any downsides for an executable package.
>>>>
>>>> Is it 'not recommended' even for executable packages? If not, then how
>>>> can I do it?
>>>>
>>>> [1]: https://wiki.haskell.org/Cabal/Developer-FAQ
>>>>
>>>> --
>>>> Regards
>>>>
>>>> Sumit Sahrawat
>>>>
>>>> _______________________________________________
>>>> Haskell-Cafe mailing list
>>>> Haskell-Cafe at haskell.org
>>>> http://mail.haskell.org/cgi-bin/mailman/listinfo/haskell-cafe
>>>>
>>>>
>>
>>
>> --
>> Regards
>>
>> Sumit Sahrawat
>>
>
>


-- 
Regards

Sumit Sahrawat
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