[Haskell-cafe] Standard package file format

David McBride toad3k at gmail.com
Fri Sep 16 12:39:15 UTC 2016

While I would personally love having a package description in haskell, I
don't think it is a good idea.

If you can't start or modify a package without already knowing haskell, it
is a huge barrier to entry.  I remember trying to get started in scala and
having a lot of trouble with sbt because I didn't know their operators for
lists and arrays or hash tables or whatever it is that they use in their

On Fri, Sep 16, 2016 at 4:57 AM, yogsototh <yann.esposito at gmail.com> wrote:

> I guess the overriding question I have here is: what is the PROBLEM being
>> solved?
> Let me share my experience with Clojure and lein. They use a clojure
> hash-map for their configuration. So yes arbitrary code could be executed
> and I believe this is a _very good thing_.
> Why? Because it makes it very easy to add sub-configuration that can be
> used by third party plugin. For example:
> - a plugin that help the use of environment variables (lein-environ) which
> is really helpful for application development (not so much for library
> development)
> - a plugin that use S3 for our private dependencies (not supported by
> default by lein)
> For deployment: we were able to add request to our API server that provide
> not only the written version but also the git commit hash. So we could be
> certain of the version of the server. Too much time there were sys/admin
> deployment errors. And that could only be achieved because we were able to
> run arbitrary command in the project description file.
> I certainly forget many other advantages of having a package description
> format which is simply a data structure in the hosted language. But this
> has by far my preference.
> - cabal is ok, but very imperfect, I generally need to have a lot of
> copy/paste, I need to change it very often while writing application with
> many dependencies
> - JSON/YAML/TOML are simply not powerful enough to match all semantics we
> might need to configure a project. For example we might want to have Set
> instead of List for some properties. Or I don't know maybe ternary tree
> structures.
> The point is: we pay a price by adding a step between the semantic and the
> syntax.
> While if our configuration format was in Haskell we could express the
> semantic more directly.
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