@Chapter Remarks on technical problems and the implementation

@Section Making the HeLP-package run
#! For all basic functionalities of the HeLP-package (using only the solver normaliz) the standard GAP-installation
#! should suffice to make everything work: Get the most recent GAP from the <URL Text="GAP-webpage">http://www.gap-system.org/</URL> 
#! by following the instructions on the Download-page. Make sure to also run <K>InstPackages.sh</K> 
#! as explained there. This should install all packages needed to run HeLP. Just start GAP and type
#! <K>LoadPackage("HeLP");</K>. In GAP 4.8.2 the NormalizInterface has to be updated to version 0.9.6 
#! or newer which can be obtained from the 
#! <URL Text="website">http://gap-packages.github.io/NormalizInterface//</URL> of the package.
#! For GAP 4.8.3 or newer this should not be necessary anymore.<P/>

#! Here is a checklist what to do, if the package does not work or you also want to use the solver 4ti2:
#! * Make sure you have sufficiently new versions of the following software: 
#!   - <URL Text="GAP">http://www.gap-system.org/</URL> (at least 4.8.2)
#!   - the GAP-package <URL Text="CTblLib">http://www.math.rwth-aachen.de/~Thomas.Breuer/ctbllib/</URL> (at least 1.2.2)
#!   - the GAP-package <URL Text="IO">http://gap-packages.github.io/io/</URL> (at least 4.2; see also the next bullet point if this package can not be loaded)
#!   - the GAP-package <URL Text="4ti2Interface">http://wwwb.math.rwth-aachen.de/~gutsche/gap_packages/4ti2Interface/</URL> (at least 2015.04.29; this package needs the IO-package)   <P/>
#!   - the GAP-package <URL Text="NormalizInterface">http://gap-packages.github.io/NormalizInterface//</URL> (at least 0.9.6)   <P/>
#!   
#!  Usually all these packages should come with a sufficiently recent GAP-installation (4.8.2 or newer)
#!  and should be contained in the pkg-folder of the GAP-installation. To see if they are working you can load them by typing
#!  <K>LoadPackage("[name]");</K> after starting GAP, where <K>[name]</K> is the name of the package.
#! * The IO-package needs a C-part to be compiled. To see if this has already been done on your system, you can enter
#!   <K>LoadPackage("IO");</K> after starting GAP. If the result is <K>fail</K> and the package is contained in the pkg-folder, than most likely the C-part is not yet compiled.
#!   For information on installation and in particular on how to compile the C-part, see the
#!   <URL Text="manual">http://gap-packages.github.io/io/doc/chap0.html</URL> (in particular Chapter 2) or the README-file of that package.<P/>
#! * The installation of normaliz is possible via the GAP-package <URL Text="NormalizInterface">http://gap-packages.github.io/NormalizInterface//</URL> (at least 0.9.6).
#!   Just access the folder in a terminal and do <K>./build-normaliz.sh; ./configure; make</K>.
#! * If you want to use 4ti2, please make sure that <URL Text="www.4ti2.de">http://www.4ti2.de</URL> (Version 1.6.5 or newer) is properly installed.
#!   In case of an error-message "The executable 'zsolve' provided by the software 4ti2 was not found." after typing <K>LoadPackage("HeLP");</K> either the software is not properly installed or
#!   installed in a directory where GAP can not find it, i.e. a directory not contained in the path-variable.  The content of this variable can typically be displayed by typing <K>echo \$PATH</K> 
#!   (Linux, Mac) <K>echo %PATH%</K> (Windows) in a terminal or a command prompt.  The manual of 4ti2 contains several pages of information on how to install the program. 
#!   Note that the installation of 4ti2 requires gcc (g++) and gmp installed
#!   (which come with many Linux installations or can be installed using a package manager).  
#!   Make sure to execute all four commands indicated in the 4ti2 manual (possibly without the <K>--prefix=</K>-part):<P/>
#!     <K>./configure --prefix=INSTALLATION-DIRECTORY</K><P/>
#!     <K>make</K><P/>
#!     <K>make check</K><P/>
#!     <K>make install-exec</K><P/>
#!   Depending on the settings of your system you might need root privileges (type <K>sudo</K> in front of every command) to unpack the files and install them.
#!   To check whether the installation worked, you can enter <K>zsolve</K> in a terminal.
#!   In case one of the required programs (g++ or gmp) was not installed when running <K>make</K>
#!   for the first time, you might need to run <K>make clean</K> and the above commands afterwards again (several times) to compile 4ti2 successfully.
#!   If you already have 4ti2 installed in a directory not contained in the path-variable and want to avoid a re-installation, in many cases the following helps:
#!   - Start a terminal and access a path written in your bash or system_bash. Typically <K>usr/local/bin</K> should work. <P/>
#!   - Run <K>ln -s /[PathToZsolve] zsolve</K>, where <K>[PathToZsolve]</K> is the path to the executable zsolve. This sets a symlink to the right place.
#!   E.g. <K>ln -s /opt/4ti2/bin/zsolve zsolve</K> was used on the (Linux) computers in Stuttgart.
#! * In case you use 4ti2, we also recommend to install <URL Text="lrslib">http://cgm.cs.mcgill.ca/~avis/C/lrs.html</URL>, at least version 4.3 
#!   (note that version 4.2 or older sometimes produces unwanted behavior).  This software provides the 'redund' command, 
#!   which can be switched on and off within HeLP, but which often leads to better performances (cf. <Ref Func='HeLP_UseRedund'/>).
#!   For installation see the User's Guide or the Readme-file on the above mentioned homepage.  Usually, after unpacking in a 
#!   directory contained in the path-variable it should be enough to call<P/> <K>make all</K><P/> (possibly as root) inside the lrslib-directory.
#! * If this does not help to get HeLP running, please feel more than welcome to contact one of the maintainers of the package.

@Section How much 4ti2 and normaliz is really there?
#! The reason, why the programs 4ti2 and normaliz are used in this package, is basically that they can solve systems 
#! of linear inequalities efficiently and there
#! exist good GAP-Interfaces for them. However there is only one line of code
#! where a function is called which accesses 4ti2 and a few more for normaliz. Thus the effort of using another solver of
#! inequalities would be not so big, if there is a GAP-Interface for it.
#! If you are aware of such a solver and would like to use it in this package,
#! please contact the authors of this package. We will be happy to help.
