bisection.lsp and falsep.lsp are from Gerald Roylance CLMATH
library.

zero.lsp is by Jan de Leeuw
;;; This implements the root finders discussed in Numerical Recipes,
;;; second edition, section 9.1 - 9.3. We add some embellishments
;;; based on Thisted, and on the FZERO routine from the various
;;; FORTRAN libraries.