Hello Andrey,
Just one more comment - hope you would not mind.
This syntax is incorrect (error message):
With this one the syntax is correct but gives problematic and questionable results:
In the first place, I was thinking that multiple assignments are problematic but I remembered that, i.e., this is quite correct:

SMath must have multiple assignments in the same math region. On the other hand I commented the issue about "local" and "global" variables - problematic "line" environment in few posts:
http://en.smath.info/forum/default.aspx?g=posts&m=3113#post3113http://en.smath.info/forum/default.aspx?g=posts&m=3114#post3114Then I remembered that Mathcad does not allow multiple assignments. I suppose because of the similar problems. In Mathcad inside the "line" blocks there are "local assignments" - left arrow character - used instead ordinary (:=) assignment operator. However, I would like very much SMath to have the functionality of multiple functions with "line" and programming (above are the mentioned posts about the present situation). At the moment I do not know how to deal with it. I feel that the solution is right there and SMath is close to it. Of course, this is just my impression.
Regards,
Radovan