PK_ERROR_code_t  PK_LOOP_ask_fins
(
--- received arguments ---
PK_LOOP_t        loop,              --- a loop

--- returned arguments ---
int       *const n_fins,            --- number of fins (>= 0)
PK_FIN_t **const fins               --- fins (optional)
)


This function returns an ordered list of fins around the given loop.


The fins are ordered nose-to-tail, so that the end of each fin coincides with
the beginning of the next fin in the list, and the end of the last fin
coincides with the start of the first.

If a fin is viewed along its direction, with the face normal pointing upwards,
the face which owns the fin's loop is to the left.

The output array fins is optional. If it is set to NULL, the function will
only compute the number of fins in the loop.