[Haskell-cafe] Additional functionality using cabal configure flags

[Konstantine Rybnikov]

In this case flags for gtk plotting support on/off do seem like a normal
choice

On Fri, Mar 13, 2015 at 9:59 AM, Sumit Sahrawat, Maths & Computing, IIT
(BHU) <sumit.sahrawat.apm13 at iitbhu.ac.in> wrote:

> 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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