quantile
Computes the quantile (inverse CDF) for the given probability p.
Uses the inverse of the piecewise quadratic CDF. For p <= (c - a) / (b - a), the result is computed from the left segment; otherwise, from the right segment.
Return
the value x at which cdf(x) = p. Returns a for p = 0 and b for p = 1.
Parameters
p
the cumulative probability, must be in [0, 1].