This is a page for myself to remind me of some functions in prolog.
A good tool for implementing prolog programm's is:
<TODO: link to SWI prolog program>
Simple family database for prolog:
female(josephien).
male(gerard).
male(marc). male(dennis).
mother(josephien, marc).
mother(josephien, dennis).
father(gerard, marc).
father(gerard, dennis).
In prolog there can be an anonymous variable "_". For example: if you want to ask if gerard is a father, the name of the son is not important. So you can use the following statement:
?- father(gerard, _).
Prolog will then answer with yes.
A variable can also be suppressed with an "_" If it's before a variable the variable will not be displayed in the result. Example:
?- father(_Vader, Child).
Child = marc.
Yes.
The following example shows how there can be asked if a father and a mother are parents of a child:
Parents(Father, Mother, Child):-
father(Father, Child),
mother(Mother, Child).
The following example shows a grandMother example:
grandMother(GrandMother, Child):-
mother(GrandMother, Mother),
mother(Mother, Child).
grandFather(GrandFather, Child):-
father(GrandFather, Father),
father(Father, Child).
Lists:
Member function:
member(X, [X|Tail]).
member(X, [Y|Tail]) :-
member(x, Tail).
Concatination:
conc([],L,L).
conc([X|L1], L2, [X|L3]):-
conc(L1, L2, L3).
Append:
Append two lists with the following structure: append(List1, List2, List1And2).
append([], List, List).
append([Element, List1], List2, [Element| List1And2]):-
append(List1, List2, List1And2).
Length:
Calculate the length of a list with the following structure: length(List, Number); Where number is the lenght of List
lenght([], 0).
length([Element|Tail], L):-
length(Tail, M),
L is M+1.
