[R] "Matrix' with Functions

[Alaios]

Dear R members,
I have a quite large of function that are named like that
f11,f12,...f15
f21,f22,...f25
..
f51,f52,...f52

These are static (hard-coded) functions that the only common they have is that they take the same number and type of input fij(a,b,c,d). As you might understand this is really close to the notion of matrix only that my 'matrix' contains functions. It would be great if I can address all these function using a numbering-scheme like F(i,j) where for example
F(1,1) will return the f11(a,b,c,d,).

I am sure that this might be quite complex to implement so could you please refer me to some book/tutorial that addresses this kind of topics?

I would like to thank you in advance for your help
Best Regards
Alex