Sander, what Bruce didn't mention in the text of his post (but which he does show in his notebook) is that one has to load the Notation` package and use the Symbolize function before using his approach.

It can be done by putting a colon between the subscripted object and the underscore.

f[ Subscript[k, 1]:_, Subscript[k, 2]:_ ] := 1- (Subscript[k, 1] Subscript[k, 2] ) / (Subscript[k, 1] - Subscript[k, 2])

Subscripted objects can be used in executable code, but doing it robustly takes work.
See the attached notebook for a mini-tutorial.

If you can postpone subscripted variables for the presentations, after the calculations are finished, it might be much less trouble.

Attachments:

Thank you all for your response.

@Bruce, I was wondering if there is something different (i.e. your suggestion still remains) if I define directly compiled function by using Compile[{a,b},a*b]. I assume that I still need to use Symbolize from the notation package? But not the colon anymore?

My intention is to later compile those function to C for later use in an C# application.

Hi Matthias,

This is generally not a good idea: WR_ (subscripted) is seen as:

Times[Blank[],Subscript[W,R]]

while WR_ (no subscript) is seen as:

Pattern[WR,Blank[]]

Which are fundamentally different. Moreover, the first argument of Pattern must be a symbol, i.e. not something with a Head different from Symbol (e.g. Subscript). Try not to use subscripts in Mathematica, it doesn't work very nice. See for example:

r=2;
r+Subscript[r, a]

outputs:

2+Subscript[2, a]

I.e. the ra (subscript) is seen as variable r with a subscript, not a new variable by itself.