CODEWITHSUNDEEP
listprolog
mll
mll

Reputation: 195

Prolog transform and separate term (atom) into a list

I have a term (more accurately an atom) like this:
name1(value1),name2(value2)
and I would like to have instead a "real" list like this:
[name1(value1), name2(value2)]
or separeted terms like this:
name1(value1) and name2(value2)
any idea on how to do it?

Upvotes: 2

Views: 2195

Answers (3)

Will Ness
Will Ness

Reputation: 71065

simple: for your list [H|T] with T=[] and H the compound term in question that is its head element, have H=','(A,B), List=[A,B].

You can even just write H=(A,B), List=[A,B]. - parentheses are mandatory here.

IOW the data term you're talking about is just an ordinary compound term, with ',' as its functor. If you don't know the structure of these terms in advance, you can inspect it with `=../2':

H =.. [Functor | Arguments].

(I see you got the same advice from @mat).

Upvotes: 1

CapelliC
CapelliC

Reputation: 60004

In Prolog we use pattern matching to apply different processing to list'elements:

change_list([], []).  % end of recursion
change_list([(T1,T2)|Ri], [T1,T2|Ro]) :-  % recursive step doing required transformation
  !, change_list(Ri, Ro).
change_list([E|Ri], [E|Ro]) :-  % catch all rule: copy elem
  change_list(Ri, Ro).

Upvotes: 1

mat
mat

Reputation: 40768

What about:

ands((A,B)) --> !, ands(A), ands(B).
ands(X)     --> [X].

Example:

?- phrase(ands((a,b,c,d)), Ls).
Ls = [a, b, c, d].

Upvotes: 3

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