im done of searching here for a solution but nothing so i decided to ask.
So, i have a query that returns in a list something like this:
List = [6-"read",3-"magazines",3-"music",1-"sport"].
And i need to perform a transformation so do i can get the list like this:
List = [read,magazines,music,sport].
or
List = ["read","magazines","music","sport"].
For that i think i should pass first the to a string to take out the numbers and the '-'. But im struggling with that.
Hope someone can help me! Thanks
This looks like homework, so I will not give you the full implementation. What you are looking for is pattern matching in a rule head:
fst_pair(X, pair(X,Y)).
The - operator is just an infix function symbol such that you could write
fst(X, X-Y).
Using this kind of pattern matching it should be easy to write a recursive predicate over the list. It must have a base case for the empty list and a step case for a head followed by the tail of the list:
fsts_list([], []).
fsts_list([ ... | TailFirsts ], [... | Pairs] ) :- % replace ... by some terms
% possibly insert some predicates here, depending on what you do above
fst_lists(TailFirsts, Pairs).
Happy solving!
