Advance notice that I'd like to make Cabal depend on parsec

Heinrich Apfelmus apfelmus at
Fri Mar 15 10:38:37 CET 2013

Duncan Coutts wrote:
> Hi folks,
> I want to give you advance notice that I would like to make Cabal depend
> on parsec. The implication is that GHC would therefore depend on parsec
> and thus it would become a core package, rather than just a HP package.
> So this would affect both GHC and the HP, though I hope not too much.
> [..]
> Why did I choose parsec? Practicality dictates that I can only use
> things in the core libraries, and the nearest thing we have to that is
> the parser lib that is in the HP. I tried to use happy but I could not
> construct a grammar/lexer combo to handle the layout (also, happy is not
> exactly known for its great error messages).

Reuse is good, but the implication I'm worried about is this: Can I 
upgrade the  parsec  package installed on my system by doing a user 
install from  hackage ? Without an implementation of more flexible 
package installations (multiple versions installed simultaneously), any 
dependency of GHC has its version number essentially set into stone.

 From this point of view, this proposal is not about making Cabal depend 
on  parsec , but about fixing the canonical version of  parsec .

Best regards,
Heinrich Apfelmus


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