narrow_by_discretes.RdWhen finding the inverse of the cdf at p, and with the solution
between low and high, this function narrows this range based
on an intermediate discrete value, and zeroes-in on that
discrete value if it's the solution.
narrow_by_discretes(distribution, p, low, high, discrete, direction)A distribution having access to a cdf.
Value of the cdf to calculate inverse at.
Single numerics specifying the lower and upper bound to look between.
Numeric value indicating a discrete point to possibly
narrow the range by. Could be NA; could have length 0; could be
outside of the range c(low, high).
One of "left" for calculating left-inverse, or
"right" for calculating right-inverse.
The benefit of this step when inverting a cdf is to return
the exact discrete value if p falls within its jump discontinuity.