i am implementing logic gates in prolog but having this error

Question

and(A,B) :- A, B.

or(A,_) :- A.
or(_,B) :- B.


error that i am getting is this

compiling C:/Users/firoz/OneDrive/Desktop/neww codes/tt.pl for byte code... C:/Users/firoz/OneDrive/Desktop/neww codes/tt.pl:10: warning: singleton variables [Expr] for do/2 C:/Users/firoz/OneDrive/Desktop/neww codes/tt.pl:11: warning: discontiguous predicate do/3 - clause ignored C:/Users/firoz/OneDrive/Desktop/neww codes/tt.pl compiled, 11 lines read - 2112 bytes written, 7 ms

Answer 1

You are missing a comma in this line:

do(_,_,Expr):- Expr,!,write(true),nl.