RealAlgebraic - a number type for exact geometric computation. Real_algebraic is a number type for exact geometric computation. It allows to compute the sign of arithmetic expressions involving the operations +, -, *, / and roots of any degree. Arithmetic expressions are recorded as directed acyclic graph (dag). Using the dag representation, an expression can be evaluated numerically several times with increasing precision, making sign computation adaptive. Real_algebraic is based on other libraries. To get a working number type you will need either LEDA (free or commercial edition) or both Boost and MPFR. We devised new efficient methods to convert expansions into arbitrary precision floating-point numbers that will be part of Real_algebraic soon.