| Sean, Here's a solution:
map(_Map, [], []). map(Map, [HIN|TIN], [HOUT|TOUT]) :- Map =..Terms, append(Terms, [HIN,HOUT], TermsExtended), MapExtended =.. TermsExtended, call(MapExtended), map(Map, TIN, TOUT).
This works 'both ways': map(lower_upper, [a,b], U) gives U=['A','B'] map(lower_upper, L, ['A','B']) gives L=[a,b].
The 'Map' can be any term where it is meaningful to append two arguments to the end of the term and evaluate the extended term.
Lindsey
I decided to write a maplist type predicate that will be used to map a function over a list and return the list of transformed values. I have wanted this for a while now and I sat down and came up with this. It works BUT I am not happy with it for reasons outlined below so any suggestions etc. are welcome.
maplist2(In, X, Out) :- transform_list(In, X, [], Out).
transform_list([], _, Acc, Final) :- reverse(Acc, Final).
transform_list([E|Es], Xfn, Acc, Final) :- Xform =.. [Xfn, E, Out], call(Xform),
transform_list(Es, Xfn, [Out|Acc], Final).
For example, if I wanted to convert a string from lower case to upper case I would have to use a list of atoms to satisfy lower_upper/2, that's not an issue. The assumption for my maplist2 is that the transformer function has arity 2 and the first paramter is the input and the second is the output.
What is the issue though is that lower_upper/2 works either way around and if I wanted to convert a->'A' or 'A'->a then how would that work?
Haskell has sections and "flip"..is there a Prolog way to say that I want to change the order of evaluation of a function if you catch my drift?
Thinking on my feet here, it would be the difference between currently passing in:
lower_upper
and then in a cool world using
lower_upper(X,_) or
lower_upper(_,X)
instead and "it" would know to replace "_" with the input parameter...I am going to see what I can come up with!
Thanks, Sean.
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