Focused on root-finding

Fast, accurate and certified root bounds (a few ulps max) in the face of any condition number or multiplicity.

Simple polynomial representation

Polynomials are represented simply with coefficients given densely as an array of numbers from highest to lowest power, where number can be any of several choices: double,bigint, double-double or Shewchuk expansions

Functional (as in functional programming)

All functions are pure. See e.g. Professor Frisby's mostly adequate guide