  The Hirsch function of a given continuous function is a new function
depending on a parameter. It exists provided some assumptions are satisfied. If
this parameter takes the value one, we obtain the well-known h-index. We prove
some properties of the Hirsch function and characterize the shape of general
functions that are Hirsch functions. We, moreover, present a formula that
enables the calculation of f, given its Hirsch function $h_f$.
