I have some doubts about the :-op operator in Prolog, because I don't know how to handle it. My exercise is focused on creating a predicate that, from an attribute-value list, whose format is [a1=>v1, a2=>v2,...,aN=>vN], obtains the value of an attribute that is Ask him.
Example: ?- value(shape, [color=>blue, shape=>spherical, weight=>light, material=>plastic], X). X=spherical.
To do this, we suggest defining the => operator in the logical base.