toSFun
Maps MST objects to SFun. Unsupported operations throw IllegalStateException.
Detailed mapping is:
MST.Numeric ->SConst;
Symbol ->SVar;
MST.Unary ->Negative, Sine, Cosine, Tangent, Power, Log;
MST.Binary ->Sum, Prod, Power.
Receiver
The node.
Return
A scalar function.