<?xml version="1.0" encoding="UTF-8"?>

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  intro.xml                HomalgToCAS package documentation              Mohamed Barakat
                                                                            Thomas Breuer
                                                                           Simon Goertzen
                                                                            Frank Luebeck

  Copyright (C) 2007-2009, Lehrstuhl B für Mathematik, RWTH-Aachen University

This chapter gives a short introduction and explains the philosophy
behind the package.

-->

<Chapter Label="intro">
<Heading>Introduction</Heading>

&HomalgToCAS; is one of the core packages of the &homalg; project
<Cite Key="homalg-project"/>. But as one of the rather technical
packages, this manual is probably not of interest for the average
uers. The average user will usually not get in direct contact with the
operations provided by this package. <P/>

Quoting from the Appendix <Ref Appendix="The Core Packages"
BookName="homalg"/> of the &homalg; package manual (&see;
<Ref Sect="HomalgToCAS" BookName="homalg"/>): <P/>

<Quoted>The package &HomalgToCAS; (which needs the &homalg; package)
includes all what is needed to let the black boxes used by &homalg;
reside in external computer algebra systems. So as mentioned above,
&HomalgToCAS; is the right place to declare the three &GAP;
representations external rings, external ring elements, and external
matrices. Still, &HomalgToCAS; is independent from the external
computer algebra system with which &GAP; will communicate <E>and</E>
independent of how this communication physically looks like.</Quoted>

<Section Label="HomalgToCAS-provides">
<Heading>&HomalgToCAS; provides ...</Heading>

<List>
  <Item>Declaration and construction of
    <List>
      <Item>external objects (which are pointers to data (rings,ring
	elements, matrices, ...) residing in external systems)</Item>
      <Item>external rings (as a new representation for the
	&GAP4;-category of homalg rings)</Item>
      <Item>external ring elements (as a new representation for the
	&GAP4;-category of homalg ring elements)</Item>
      <Item>external matrices (as a new representation for the
	&GAP4;-category of homalg matrices)</Item>
    </List>
  </Item>
  <Item><C>LaunchCAS</C>: the standard interface used by &homalg; to launch
    external systems</Item>
  <Item><C>TerminateCAS</C>: the standard interface used by &homalg; to
    terminate external systems</Item>
  <Item><C>homalgSendBlocking</C>: the standard interface used by &homalg; to
    send commands to external systems</Item>
  <Item>External garbage collection: delete the data in the external
    systems that became obsolete for &homalg;</Item>
  <Item><C>homalgIOMode</C>: decide how much of the communication you
    want to see</Item>
</List>

</Section>

</Chapter>