George Russell writes:
> Well that's a big question. As I understand it, the errant value,
> lvl20, is a string representing an error message (which I suppose is to
> be thrown in the event of a matching failure). Since it should
> only be used on error, surely there is no speed benefit to inlining it,
> and probably there is a space penalty (since you store the string
> multiple times). In this case there is a very real disadvantage, since
> inlining forces everything that imports that module to recompile. So
> my suggestion would be that values required only for errors should never
> be inlined or put in a .hi file.
I agree so wholeheartedly that I just write a (very!) short paper on
the subject for ICFP (having discovered to my surprise that no such
write-up existed). It describes how to identify such expressions and
hoist them out so they don't end up getting inlined. It's still being
refereed is thus likely to be revised, but if you're interested in a
pre-print take a look (there are no pointers to it from elsewhere at
the moment):
@unpublished{bottomExtract,
AUTHOR = {Jan-Willem Maessen},
YEAR = {1999},
month = Mar,
TITLE = {Bottom Extraction: Factoring error handling out of
functional programs},
documentURL = "http://www.csg.lcs.mit.edu/~earwig/extraction.ps"
note = {Submitted to ICFP 2000}
}
-Jan-Willem Maessen
