This function is intended for package developers, not end-users. Canonically, mosaicCalc functions that produce layerable graphics have
three initial arguments in a specific order: (1) a previous gg layer, (2) a tilde expression, and (3)
a domain. But either (1) or (3) can be missing. first_three_args() translates a leading
... argument into the list of the canonical three initial arguments, returning them
as components of a list. In addition, there may be additional arguments
in ... that specify other aspects of the plot, e.g. color.
first_three_args(..., two_tildes = FALSE)unnamed arguments to be translated into a list with the three canonical arguments and any other arguments not named explicitly in the parent function definition.
if TRUE then look for the first FOUR arguments, the middle
two of which will be tilde expressions.
In constructing a mosaicCalc graphics layer, the function (e.g. slice_plot() or contour_plot())
whould have ... as its first argument. Intercept that ... with first_three_args() to
extract the first three canonical arguments as components gg, tilde, and domain of a
list. Any remaining arguments in ... will be placed in the dots component.