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Mount Shasta is a 4317-meter somewhat active volcano in Northern California.
Its snow-capped multiple-crater summit, which appears on the cover of this
guide^{1}is a well-known california landmark as well as a ski resort.
This guide describes however SHASTA, an interactive interface to
the
library that provides some efficient computations revolving
around difference operators and systems in
or
. In fact, the
main goal of SHASTA is to provide access to selected functionalities
of the
library to other computer algebra systems, or to users
who do not own an `Aldor` compiler, or who feel more confortable with
interactive access to a library. The functionalities currently provided
by SHASTA are the ones that tend to be missing from several commercial
computer algebra systems, namely:
- Basic arithmetic in
, including
adjoints and left and right gcd's and lcm's.
- Exterior powers.
- Rational kernels,
*i.e.*
for
,
and rational solutions of inhomogeneous equations of the form
.
- Rational kernels of systems of the form
.
- Hypergeometric solutions,
*i.e.* the solutions of
such that
.
- Factorisation and decomposition of second and third-order operators.

If you do not need any of the above computations, then
you probably will not have much use for SHASTA.
Otherwise, since SHASTA provides implementations of several recent
algorithms for those computations, it is worth trying it and
reading further.

** Next:** How do I get
** Up:** Introduction
** Previous:** Introduction
** Contents**
** Index**
Manuel Bronstein
2002-09-04