Declaring curcontext etc local is superfluous as _arguments states are
not used. It is also superfluous to include an outer function definition
syntax in zsh autoloadable functions. Zsh convention is not to
capitalize descriptions. It is also better to use the imperative mood
verb form for descriptions as this allows them to start with the
shortest form of the verb - e.g. "reduce" instead of "reduces" and
results in better grammar in the absence of a sentence subject. I'd
recommend this in the --help output too. Using _guard for the position
and dimensions was unnecessary given that the values are not mixed with
other matches.