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% Copyright The Numerical Algorithms Group Limited 1992-94. All rights reserved.
% !! DO NOT MODIFY THIS FILE BY HAND !! Created by ht.awk.
\newcommand{\XPolynomialXmpTitle}{XPolynomial}
\newcommand{\XPolynomialXmpNumber}{9.89}
%
% =====================================================================
\begin{page}{XPolynomialXmpPage}{9.89 XPolynomial}
% =====================================================================
\beginscroll
The \spadtype{XPolynomial} domain constructor implements multivariate polynomials
whose set of variables is \spadtype{Symbol}.
These variables do not commute.
The only parameter of this construtor is
the coefficient ring which may be non-commutative.
However, coefficients and variables commute.
The representation of the polynomials is recursive.
The abbreviation for \spadtype{XPolynomial} is \spadtype{XPOLY}.
Other constructors like \spadtype{XPolynomialRing}, \spadtype{XRecursivePolynomial}
\spadtype{XDistributedPolynomial},
\spadtype{LiePolynomial} and
\spadtype{XPBWPolynomial}
implement multivariate polynomials
in non-commutative variables.
We illustrate now some of the facilities of the \spadtype{XPOLY} domain constructor.
\xtc{
Define a polynomial ring over the integers.
}{
\spadpaste{poly := XPolynomial(Integer) \bound{poly}}
}
\xtc{
Define a first polynomial,
}{
\spadpaste{pr: poly := 2*x + 3*y-5 \free{poly} \bound{pr}}
}
\xtc{
and a second one.
}{
\spadpaste{pr2: poly := pr*pr \free{poly} \bound{pr2}}
}
\xtc{
Rewrite {\bf pr} in a distributive way,
}{
\spadpaste{pd := expand pr \free{pr} \bound{pd}}
}
\xtc{
compute its square,
}{
\spadpaste{pd2 := pd*pd \free{pd} \bound{pd2}}
}
\xtc{
and checks that:
}{
\spadpaste{expand(pr2) - pd2 \free{pr2} \free{pd2}}
}
\xtc{
We define:
}{
\spadpaste{qr := pr**3 \free{pr} \bound{qr}}
}
\xtc{
and:
}{
\spadpaste{qd := pd**3 \free{pd} \bound{qd}}
}
\xtc{
We truncate {\bf qd} at degree {\bf 3}:
}{
\spadpaste{ trunc(qd,2) \free{qd}}
}
\xtc{
The same for {\bf qr}:
}{
\spadpaste{trunc(qr,2) \free{qr}}
}
\xtc{
We define:
}{
\spadpaste{Word := OrderedFreeMonoid Symbol \bound{Word}}
}
\xtc{
and:
}{
\spadpaste{w: Word := x*y**2 \free{Word} \bound{w}}
}
\xtc{
The we can compute the right-quotient of {\bf qr} by {\bf r}:
}{
\spadpaste{rquo(qr,w) \free{qr} \free{w}}
}
\xtc{
and the shuffle-product of {\bf pr} by {\bf r}:
}{
\spadpaste{sh(pr,w::poly) \free{pr} \free{w}}
}
\endscroll
\autobuttons
\end{page}
%
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