PPT Slide

/* append3( List1, List2, Result ) */

append3( [ ] , Alist , Alist ) .

append3( [ First | Rest1 ] , Alist , [ First | Rest2 ] ) : -

append3( Rest1 , Alist , Rest2 ) .

| ? - append3( [ a , b , c , d ] , [ e , f , g , h ] , X ] .

X = [ a , b , c , d , e , f , g , h ]

| ? - trace.

append3( [ a , b ] , [ c , d ] , R ) .

0 Call: append3( [ a , b ] , [ c , d ] , __ 410 )

1 Call: append3( [ b ] , [ c , d ] , __ 534 )

2 Call: append3( [ ] , [ c , d ] , __ 566 )

2 Exit: append3( [ ] , [ c , d ] , [ c , d ] )

1 Exit: append3( [ b ] , [ c , d ] , [ b , c , d ] )

0 Exit: append3( [ a , b ] , [ c , d ] , [ a , b , c , d ] )

R = [ a , b , c , d ]