[Haskell-cafe] where to put general-purpose utility functions

John Meacham john at repetae.net
Thu Jan 26 04:44:57 CET 2012

That is one of the wonderful things about haskell, most languages have
a negative correlation between codesize and productivity, however with
haskell there is a strong positive correlation. You can re-use so much
that as your code base grows it becomes easier to add new features
rather than harder.

I solve that problem by having a darcs repository for all my utility
modules, then when I want to use them in a project, I just 'darcs
pull' them into the current repository and they appear. as long as a
patch doesn't cross the boundry between the utility modules and the
rest of the codebase I can push changes upstream to the utility
repository from my specific project, or pull in new improvements to
the utility functions. I can also make local modifications to the
utility modules and just not push the local modifications upstream if
needed. The cool thing is that the darcs history has the merged
history of my projects, and tagging with a version number or release
will snapshot both your program and the exact version of the utility
routines used at that time.

The ability to have multiple "sibling" darcs repositories is a really
powerful feature. quite handy.

I had a similar system before darcs where I used a shared RCS
directory between projects, but that wasn't nearly as seamless or

Plus it makes it easier when collaborating, as far as anyone is
concerned, the project is a single darcs repository they can get and
build and create patches for. The fact that behind the scenes it is
actually a collection of repositories spawning patches. modifying
them, and exchanging them in a bizarre parody of bacterial plasmid
exchange* is completely transparent.


* stolen prose, I just liked the sound of it.

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