Question: Invalid operator parameter name

Dear Maple users

Please help me correct this input:

> f := (c[A], c[B]) -> c[A]+c[B];
Error, invalid operator parameter name
    f Assign Typesetting:-mambiguous(

      (c[A]comma c[B]) rarr c[A] + c[B], 

      Typesetting:-merror(invalid operator parameter name))
> 

In Maple, c[A] is actually "c subscript A".

Thanks for help.

PS: Is there now way to include Maple 2D Math input here in the forum?