ConstantList

Which names the language reads as mathematical constants, and what each is worth
-- asked at the moment of evaluation, so that the digits are the current
precision's and not those of whichever context was set when this class was
initialised (https://github.com/asc-community/AngouriMath/issues/1367), and a
Real whatever the downcasting says: through the conversion from a
decimal, with the downcasting off, e was a Complex with a
zero imaginary part, and cached on the constant that made sgn(e^x - 1) not real-valued and e^x not the exponential of x for the rest of
the process. This is the whole registry: a name is a constant exactly when it
is a key here, and nothing below asks about pi or e by name.