====== Sister ======
{{tag>family}}
===== Description =====
Checking if two woman are sisters

**Source**:  PROLOG str.19 Wydawnictwo PLJ Warszawa 1991 ISBN 83-85190-63-5
===== Download =====
Program source code: {{sister.pl}}
===== Listing =====
<code prolog>
kobieta(kasia).
kobieta(justyna).
rodzice(stefan, maria, kasia).
rodzice(stefan, maria, justyna).

siostra(S, X) :- kobieta(S), rodzice(Ojciec, Matka, S), rodzice(Ojciec, Matka, X).</code>
===== Comments =====