Defining a function with variable in subscript

Question

I want to define function f_n:=x^n in maple in such a way that if i enter f_3 is should get x^3. i'm unable to do so, please help me in this regard. Thank you in advance.

Answer 1

There are two types of indeces - literal (a__n) and indexed (a[n]) - but neither works in the way you want as far as I know.

You can define a two variable function: f:=(n,x)->x^n. This should work the way you want. E.g. an $f_3(x)$ would be accessed as f(3,x).

The two variable function will not show in indexed notation, but except for that it should provide what want.

Answer 2

Here is one way of using a procedure call of an indexed name.

f := proc(x)
  if procname::indexed then
    x^op(1,procname);
  else error "procedure name called without an index";
  end if;
end proc:

f[3](x);

           3
          x

f[-2](x);

          1
         ----
           2
          x

f[a](x);

           a
          x

f(x);
Error, (in f) procedure name called without an index

If you are operating in 2D Input mode in the Maple GUI (its default) then in the following way you can enter an indexed name that appears as a subscripted name. Example, for the 2D Input of f[3] to appear as f-subscripted-by-3 you can enter these keystrokes:

f CtlShift_ 3 ie. Ctl-Shift-underscore together

That is quite different from the keystrokes,

f __ 3 , ie. f__3

which produces a special kind of name that (by design) gets prettyprinted as subscripted.