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# Howto append to a list recursively

## Howto append to a list recursively

(OP)
I am trying to write a prolog snippet which will find the relations between entities. I have this:

related(a,b,ab).
related(b,c,bc).
related(c,d,cd).
relation(X,Y,Z):-related(X,A,G),related(A,Y,H),Z=[G,H].

relation(X,Y,Z).
X=a, Y=b, Z=ab
X=b, Y=c, Z=bc
etc. for the trivial cases and then:
X=a, Y=c, Z=[ab,bc]
X=b, Y=d, Z=[bc,cd]
X=a, Y=D, Z=[ab,bc,cd]

Is there a kind soul who could help me out?

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