Reset variables

[blckwtr]

I have defined a function, and found a solution for a specific varable. However, with an additional boundary value, there is a new solution, found with another method. (the variable changes value). How can i reset the variable?

Let's say: r=0.3

f(r)=something

reset r

f(r)=f(r)

 

[jghrist]

Why not:
r:=0.3
f(r)=something
r:=0.4
f(r)=something else
?