Quickly recalling the definition of a temporary function to make minor edits?

edit

Another option, in addition to @tmonteil's nice answer: once you've defined f, you can do this:

sage: ed f

(%ed f or edit(f) should accomplish the same thing.) This will open up an editor window (editor based on the setting of the EDITOR environment variable, which of course should be emacs). Then you can modify f however you like.

The double question mark will show the code of f:

sage: f??
Signature: f(x)
Source:   
def f(x):
    return R(x**Integer(3)-x+Integer(188))
File:      ~/sage/9.3.develop/<ipython-input-2-567a043781c3>
Type:      function

Note that Sage's preparser has turned x^3-x+188 into x**Integer(3)-x+Integer(188).

EDIT: the above does not answer to the question: it's a quick way to recall the definition of f but it does not allow to edit it. See @tmonteil 's answer for this.

I think that the simple way is to add a condition in the definition.

R=2
def f(x,n):
       if n==1 :
        return R*(x^3-x+188)
       else :
        return R*(x^3-x+376) 

show(f(2,1),',',f(2,2))