Prolog problems

I use swi prolog. My code runs for first lin开发者_运维技巧e but it doesn't run the others.

 see(Data), //open file to read
   repeat,
    readln(A), //read line from file 
    write(A),
   A\==end_of_file,!.

I get an unexpected end of file error. Do you have any idea?

readln/1 is not a in the swi-prolog manual so maybe you should include the code for that too. assuming that it does what you say, the code should probably be:

 see(Data), //open file to read
   repeat,
   readln(A), //read line from file 
   write(A),
   A=end_of_file,!.

the repeat/0 "structure" works like repeat...until

on a side note, i would prefer recursive solution...like

io(end_of_file):-
    write(end_of_file).
io(_):-
    readln(A),
    write(A),
    io(A).

feels more declarative.