# Revision history [back]

If you remove the comment, you have to replace sgn(SGN) with sgn(SGN(x)).

For me, the problem is in:

show(SGN.parent())


That prints SR, while we have:

SGN.parent()
Callable function ring with argument x

SGN(x).parent()
Symbolic Ring


If you remove the comment, you have to replace sgn(SGN) with sgn(SGN(x)).

For me, the problem is in:

show(SGN.parent())


That prints (LaTeX) SR, while we have:

SGN.parent()
Callable function ring with argument x

SGN(x).parent()
Symbolic Ring