# Revision history [back]

Not surprised that f(3) is giving you an error. This form of substituting values in symbolic expressions has been deprecated for quite a while (well, over four years!). You must have got the warning at some point in your calculations. You should be using either f.subs(x=3) or f(x=3), i.e., specify the variable name explicitly.

Note that there are some idiosyncrasies while working with symbolic functions. For instance the following will not complain even though f is not defined as a function of x:

sage: f = SR(1)
sage: f.subs(x=2)
1


Not surprised that f(3) is giving you an error. This form of substituting values in symbolic expressions has been deprecated for quite a while (well, over four years!). You must have got the warning at some point in your calculations. You should be using either f.subs(x=3) or f(x=3), i.e., specify the variable name explicitly.

Note that there are some idiosyncrasies while working with symbolic functions. expressions. For instance the following will not complain even though f is not defined as a function of x:

sage: f = SR(1)
sage: f.subs(x=2)
1