Re: [Haskell-cafe] Additional functionality using cabal configure flags

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) 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 wrote:

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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) wrote:

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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 wrote:

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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)" написав:

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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

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-- Regards

Sumit Sahrawat

-- Regards

Sumit Sahrawat