another 'false' problem

[jonison]

hi, everyone, I have another problem now, a bit confused now.
Here is the code:

sumY(X1,[[X,Y]|Rest],Sum0,Sum) :-
X =:= X1,
Sum is Y+Sum0,
nl,write(Sum),write('##'),nl,
sumY(X1,Rest,Sum,Sum).

sumY(X1,[[X,Y]|Rest],Sum0,Sum) :-
X =\= X1,
Sum is Sum0,
nl,write(Sum0),write(' @ '),write(Sum),write(' *** '),nl,
sumY(X1,Rest,Sum0,Sum).

sumY(X1,[],Sum,Sum).

and I run this code as:

run :-
sumY(1,[[3,4],[1,1],[1,3],[3,3],[1,8]],0,Sum),
nl,write(Sum),nl.

the result shows as:

false.

could you give me suggestions on how to make this code work? Special thanks for giving me explainations on this.
Thank you for your answer, thank you!

 

[joel76]

What do you expect ?
Can you explain what the code should do ?