GAP (crime) - Chapter 1: Introduction

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1 Introduction
1.1 Installation and Loading
1.2 For Further Information

### 1 Introduction

#### 1.1 Installation and Loading

Like other GAP packages, you download and unpack this package into GAP's `pkg` directory. For example, if you were running GAP on some machine with a Unix-based operating system and GAP were installed in the directory `/usr/local/gap4r5` then you would do the following to install CRIME.

    $ cd /usr/local/gap4r5/pkg
    $ su
    % wget ftp://ftp.gap-system.org/pub/gap/gap4/tar.gz/packages/crime-1.4.tar.gz
    % gunzip crime-1.4.tar.gz
    % tar xvvf crime-1.4.tar

In this situation, users would load the package with the `LoadPackage` command.

    $ gap
    gap> LoadPackage("crime");

Users not having root access, using someone else's computer, or having bad relationships with their network administrators, could install the package into their home directories or into some other writable directory such as `/tmp` and load the package as follows.

    $ mkdir /tmp/pkg
    $ cd /tmp/pkg
    $ wget ftp://ftp.gap-system.org/pub/gap/gap4/tar.gz/packages/crime-1.4.tar.gz
    $ gunzip crime-1.4.tar.gz
    $ tar xvvf crime-1.4.tar
    $ gap -l ';/tmp'
    gap> LoadPackage("crime");

Even simpler, users can simply install the package in the `~/.gap` directory as follows.

    $ mkdir -p ~/.gap/pkg
    $ cd ~/.gap/pkg
    $ wget ftp://ftp.gap-system.org/pub/gap/gap4/tar.gz/packages/crime-1.4.tar.gz
    $ gunzip crime-1.4.tar.gz
    $ tar xvvf crime-1.4.tar
    $ gap
    gap> LoadPackage("crime");

Finally, it would be a good idea to run the test file to confirm that all the functions work properly. This can be accomplished using GAP's somewhat obfuscated but system-independent file-manipulation commands as follows.

    gap> P:=PackageInfo("crime")[1];;
    gap> D:=Directory(P.InstallationPath);;
    gap> F:=Filename(D,"tst");;
    gap> D:=Directory(F);;
    gap> F:=Filename(D,"test.g");;
    gap> ReadTest(F);

You can count yourself lucky if GAP doesn't complain about anything. There is also a longer running test file for those having ample free time described in Appendix B.

#### 1.2 For Further Information

The file `doc/example.*` contains the step-by-step CRIME calculation of the cohomology ring of the quaternion group. The file `doc/explanation.*` contains a theoretical description of how the package calculates the various cohomology products. Users wishing to read the source code can print all the programs in the `gap` directory with the program `gap/print.pl` which should be executed in the `gap` directory.

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