20 Feb
2006
20 Feb
'06
11:36 p.m.
There is a more straightforward way to get localized error messages rather than using 'maybe' and hand-writing an appropriate error, and that is to rely on irrefutable bindings. f x = ... y ... where Just y = Map.lookup x theMap now if the lookup fails you automatically get an error message pointing to the exact line number of the failure. or if the failure message of the routine is more important than the source location you can do f x = ... y ... where Identity y = Map.lookup x theMap it is anoying you have to make a choice between these two possibilities, but this can be mitigated with CPP magic or the SRCLOC_ANNOTATE pragma. John -- John Meacham - ⑆repetae.net⑆john⑈