A method of performing numerical computations in a mathematical system
with at least one function, including expressing the mathematical system
in discrete terms, expressing at least one variable of the mathematical
system as a fixed-point number, performing the computations in such a way
that the computations include the at least one variable expressed as a
fixed-point number, obtaining, from the computations, a resulting number,
the resulting number representing at least one of at least a part of a
solution to the mathematical system, and a number usable in further
computations involved in the numerical solution of the mathematical
system, and extracting a set of data which represents at least one of a
subset of digits of the resulting number, and a subset of digits of a
number derived from the resulting number.