Description: Concatenation of fixed length strings. (This special case of ccatlid is provided to complete the pattern s0s1 , df-s2 , df-s3 , ...) (Contributed by Mario Carneiro, 28-Feb-2016)
|- <" A "> = ( (/) ++ <" A "> )
|- <" A "> e. Word _V
|- ( <" A "> e. Word _V -> ( (/) ++ <" A "> ) = <" A "> )
|- ( (/) ++ <" A "> ) = <" A ">