Re: [Haskell-cafe] Generating Code

On Fri, Dec 9, 2011 at 9:17 PM, Erik Hesselink wrote:

On Fri, Dec 9, 2011 at 20:45, L Corbijn wrote:

...

So I'm interested if there are other libraries that are more suitable to the task of generating haskell code for library use, and thus generate 'human readable' exported code (so no TH). I'm also interested in how other projects generate code for their packages.

Since you ask how other packages solve this problem, and since most packages use template haskell, I have to ask: why can't you use template haskell for this?

Another option (also not code generation, but very useful in reducing boilerplate) is generic programming, for example using the 'regular' package, or the new generics in GHC 7.2.

Erik

That's a good question, and maybe I should have answered it the first place. The short answer is, I'm trying to generate modules from scratch (or spec) so there is no module yet to put the template haskell in. But I think, with my limited knowledge of template haskell, that it tries to solve a different problem, to explain it more detailed I'll first elaborate on the problem that I want to solve. I'm trying to do, in general, is generating a package (almost) from scratch by using a specification of what it should be. The specific problem is that the OpenGLRaw package is quite out of date and needs updating. This package is in essence a large FFI import of the OpenGL specification from C. To update it (or recreate it), with it's hundreds of functions and enumeration values, is not only boring but also tedious and error prone work. As there is a specification of all this a better option would be to generate it. The starting point for such generator would be only with a few helper functions and the OpenGL specification. It would then generate all the enumeration values and function imports (split over several modules). The major set of problems for using template haskell is that it doesn't have the correct features, or better said it tries to solve another problem. Template haskell generates code into an existing module, while for this problem there is no module yet to generate it into. Of course I could generate those modules and let template haskell make the FFI imports, but then the problem remains how to generate those modules. So template haskell seems (as I see it) to solve the problem of writing almost the same code twice by generating it from some parameters coded in some source file. Another problem is that the export and import lists of the modules need to be generated too and this seems not an option for TH. Lars