So nice X_Y when it accepts, so deceptive in elementary math.
erf(x) is not scalar in Smath.
In fact a very involved approximation [Mathematica 4.0]

Problem with erf(x) appears when you use functions from external plugins in the region directly. I will see if it is possible to solve the problem in the general case.

Wrote

Problem with erf(x) appears when you use functions from external plugins in the region directly. I will see if it is possible to solve the problem in the general case.

Thanks Viacheslav,
In the mean time, attached doctoring may apply to other SS.