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?
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