[Haskell-cafe] Files and Modules

Sylvain Henry sylvain at haskus.fr
Mon Dec 2 12:31:55 UTC 2024


It's not ridiculous. I would also like the GHC API to abstract over the 
file system so that I can store modules in a DB. It would require quite 
a lot of refactoring though...

Sylvain


On 02/12/2024 10:16, julian getcontented.com.au wrote:
> In a recent project that compiles Haskell source from data (ie of type Text from the module Data.Text), it would be useful to be able to decouple the dependency between GHC’s notion of where modules are and the file system. This doesn’t seem to be programmatically controllable.
>
> How tenable is this? Would it be useful for anyone else to have compilation itself be more first class in the language? If I think about languages such as LISP/Racket/Clojure, there’s a certain flexibility there that Haskell lacks, but it’s not apparent why, other than historical reasons? Would this imply changing compiling and linking into a different Monad than IO?
>
> At the moment to compile some source that exists in Text, my system has to write a bunch of temp files including the Text that contains the main module, and then put other modules in directories named a certain way, run the compiler across them via some exec command to call GHC or stack externally, then read the resulting executable back off disk to store it in its final destination.
>
> It might be useful to be able to do this from within Haskell code directly, partly similarly to how the hint library works. Though, in this case it would almost certainly also require being able to have two versions of GHC loaded at once, which would also imply being able to simultaneously have multiple or different versions of libraries loaded at once, too, and possibly also just from data, ie not from disk. It feels like a massive, massive project at that point, though, like we’d be putting an entire dependency system into a first-class programmable context. I’m still interested in what folks think about these ideas, though, event though we this may never eventuate.
>
> Does it seem to anyone else like abstracting the library and module-access capabilities of compilation so that it’s polymorphic over where it gets its data from might be useful? Is this just ridiculous? Does this step into Backpack's territory? From memory, the Haskell report doesn’t specify that modules necessarily need to be tied to the file system, but I think GHC imposes one file per module and that it be one the FS.
>
> Julian
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