On 1/17/08, Albert Y. C. Lai
Magnus Therning wrote:
This might seem like a silly question, but what's the reasoning behind the following behaviour?
% ghc-pkg list dataenc /usr/lib/ghc-6.8.2/package.conf: % ghc --make -hide-package dataenc -isrc UT.hs ghc-6.8.2 : unknown package: dataenc
Hiding an uninstalled package doesn't seem to warrant failing compilation!
"I cannot find it, therefore I cannot hide it"? XD
The following is fairly widely accepted behaviour:
$ rm phd-thsies rm: cannot remove `phd-thsies': No such file or directory
If a file is absent and you want it absent, is that an error?
(Now you might get into a long thread debating whether deletion is analogous to hiding...)
If I want to hide or delete something, and the computer can't find that something, it may be because I have a typo. If the computer remains silent about it, I fail to hide or delete the true thing. I want to delete phd-thesis, but I typed phd-thsies, and I appreciate the error report. If I fail to delete phd-thesis, at worst more people read it and be enlightened :) but if I fail to hide a package and I don't know about it, the ensuing problems will be much more mysterious.
Fair enough. I stumbled on this behaviour because I was writing a makefile for my unit/quickcheck tests. I need to make sure that the correct module is used, hence I need to hide it if it's installed. I ended up with the following in order to work around the issue: ifeq (,$(shell ghc-pkg list dataenc | grep dataenc)) GHCOPTS = -fhpc -isrc else GHCOPTS = -fhpc -hide-package dataenc -isrc endif % : %.hs ghc --make $(GHCOPTS) $< Is there a better way to do it? /M