TRYING OUT ALL VALUES to get a true result is the HEART of PROLOG

Here we do it in an imperative language with small code


nephew3 brad [?]

YES
nelly nellyson



--------------------------- TRACE --------------------

4 nephew3 brad
P=brad
nephew3 brad

4 1 sibling P A
6 sibling brad A
A=mary
sibling brad mary

4 2 if
4 3 kid A B
4 8 clear A
4 9 clear B
4 10 next
4 11 nephew3 P
4 nephew3 brad
P=brad
nephew3 brad

4 1 sibling P A
7 sibling brad A
A=nelly
sibling brad nelly

4 2 if
4 3 kid A B
10 kid nelly B
B=nellyson
kid nelly nellyson

4 4 print A
4 5 print B
4 6 echo newline
4 7 endif
4 8 clear A
4 9 clear B
4 10 next
4 11 nephew3 P
4 nephew3 brad
P=brad
nephew3 brad

4 1 sibling P A


-------------------------- CODE -------------------------


THIS IS LIKE

nephew(N K)
:-
sibling(N A)
kid(A K)


------

nephew3 P
-sibling P A
-if
-kid A B
-print A
-print B
-echo newline
-endif
-clear A
-clear B
-next
-nephew3 P

sibling alan zeta
sibling brad mary
sibling brad nelly
sibling carl tom
kid alan joe
kid nelly nellyson

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