As we have said, it is hard to know exactly which metrical position is the catalectic one, so we follow traditional analyses and assume it is the last, since catalexis (like extrametricality) seems to target final constituents rather than initial ones, at least in phonology (Kiparsky 1991).
For one thing, the clearest case of catalexis in Greek stichic meter, iambic tetrameter catalectic, has initial catalexis, not final.
We simply don't know at this point whether the catalectic position is line-initial or line-final.
In the cases at hand we need to define what it is to be anapestic dimeter, anapestic dimeter catalectic, and anapestic tetrameter catalectic.
Moving on to the catalectic version of anapestic dimeter that we find at the end of most dimeter systems, we note that it has one less filled metrical position than we expect a dimeter to have.
We capture this formally by noting that a catalectic meter intentionally violates FILL.
The formalism is to be read `a line is catalectic (C) if it violates the constraint FILL'.
Anapestic tetrameter catalectic is still rhythmically unmarked, but it now has two peculiarities in terms of length: it is twice as long as we would expect it to be (if it were a dimeter) and it has one less metrical position than we'd expect it to have (binary meters always have an even number of metrical positions).
The marked parts of anapestic tetrameter catalectic are thus just being catalectic, (35), and being a tetrameter, (37), which are enough to distinguish a catalectic tetrameter from the unmarked dimeter.
The distinctive violation of FILL in a catalectic meter occurs in the evaluation of full lines.
A catalectic line is supposed to have an unfilled metrical position and candidate (a) does not.
We turn now to iambic meters, which come in two common forms: a simple trimeter and a tetrameter catalectic (also called trochaic tetrameter).