Wed Apr 25 09:47:50 EDT 2012
Params with defaults
Find a different approach to do this:
alpha = execState (forM attrs scan) False where
scan Alpha = put True
scan _ = return ()
which sets a default and picks overwrites it with the last matching
attrib in the list (if any).
Trouble: this seems to requre a default case (scan _). Is it possible
to do it in a different way such that this default case can be
abstracted? I.e. can mismatches be mapped to nothing instead of
raising an error?