a = block.face.extra(bfp<,i>)
block.face.extra(bfp<,i>) = a

Get/set the data stored in the extra variable at index i for a face. The value in an extra variable can by any valid FISH type.

Returns:a - value
Accepts:a - value
Arguments:bfp - block face pointer i - the optional index of the extra variable to set or retrieve. Can be from 1 to 128. If not specified, 1 is assumed.