gap software package provides computer algebra system for Groups, Algorithms and Programming, you can install in your Debian 9 (Stretch) by running the commands given below on the terminal,
$ sudo apt-get update $ sudo apt-get install gap
gap is installed in your system.
Make ensure the gap package were installed using the commands given below,
$ sudo dpkg-query -l | grep gap *
You will get with gap package name, version, architecture and description in a table
| Distro | Debian 9 stretch |
| Section | Mathematics |
| Package | gap |
| Version | 4r8p5-1 |
| Description | computer algebra system for Groups, Algorithms and Programming |
| Sub Section | Math |