''Why is the interval package accurate?''
Some basic operations are provided by the C library with directed rounding and correctly rounded result: plus, minus, division, multiplication and square root.
These are used to build the most basic interval functions.
All other GNU Octave arithmetic functions are not guaranteed to produce accurate results, because they are based on C99 floating-point routines [http://www.gnu.org/software/libc/manual/html_node/Errors-in-Math-Functions.html#Errors-in-Math-Functions]. Their results depend on hardware, system libraries and compilation options. The interval package handles these functions with the help of the [http://www.mpfr.org/ GNU MPFR library]. With MPFR it is possible to compute valid and tight enclosure of the correct results.
== Quick start introduction ==