Prolog syntax and predicate logic

Question

I have 2 exception at point (THIS-RTE) and (Other-RTE) i can not manage to fix it can any1 give me a hint about what am i doing wrong, because I'm pretty sure i mess something up. Thanks

decomp([],[],0,0).
decomp([E|T],R,P,I):-
    0 is mod(E,2),
    decomp(T,R1,P1,I),
    R is [E|R1],    %**(*THIS-RTE*)** ERROR: is/2: Type error: `[]' expected, found `[2|_G7167]' ("x" must hold one character)
    P is 1 + P1.
decomp([E|T],R,P,I):-
    not(0 is mod(E,2)),
    decomp(T,R1,P,I1),
    R is append(E,R1,R), %**(*Other-RTE*)** ERROR: d:/../../../../lab1a.pro:47: evaluable `append(_G5550,_G5551,_G5552)' does not exist, but my clause is right ther
    I is 1 + I1.

append(E,[],[E]).
append(E,[A|St],[A|Et]):-
    append(E,St,Et).

Answer 1

Your syntax is a little off:

• R is append(E,R1,R) should be simply append(E,R1,R) because you are passing R
• R is [E|R1] should go directly into the header of the rule

The result should look like this:

decomp([],[],0,0).
decomp([E|T], [E|R1], P, I):-
    0 is E mod 2,
    decomp(T,R1,P1,I),
    P is 1 + P1.
decomp([E|T],R,P,I):-
    1 is E mod 2,
    decomp(T,R1,P,I1),
    append(E,R1,R),
    I is 1 + I1.

Demo.