This function is doing two things that makes it confusing, and maybe even incorrect. On is to determine a non-constraint expression is a constant, and the other is to determine whither a constraint is contradictory (1=0) or something a long those lines.
This function is doing two things that makes it confusing, and maybe even incorrect. On is to determine a non-constraint expression is a constant, and the other is to determine whither a constraint is contradictory (1=0) or something a long those lines.