Function fringe_to_ansi 

pub const fn fringe_to_ansi(j: u32) -> u32

The ANSI index of the mode carrying Fringe index j.

The Fringe counterpart of noll_to_ansi, and the more valuable of the two: Fringe orders by spatial frequency rather than radial degree, so the mapping reorders modes rather than merely renumbering them, and no amount of staring at a coefficient vector reveals a missing conversion.

Note that a Fringe index can name a mode of higher radial degree than an ANSI truncation of the same length contains (Fringe 9 is (4, 0), ANSI index 12), so check the result against the basis length rather than assuming it fits.

Panics

If j is zero. Fringe indices start at 1.