I'm starting to think that I don't know how to use my own defined operators :-( Should this tiny program work? : ****************************** uses vectores; var a, b, c : TVector; begin a.x:=1; a.y:=2; a.z:=3; b.x:=4; b.y:=5; b.z:=6; c:=a-b; writeln(c.x); writeln(c.y); writeln(c.z); end. ********************* 'cause I still get the same error. The error is in the line c:=a-b "invalid operands to binary -". Thanks again, Ariel. --- Ariel Bendersky bender@einstein.com.ar