coq software package provides proof assistant for higher-order logic (toplevel and compiler), 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 coq
coq is installed in your system.
Make ensure the coq package were installed using the commands given below,
$ sudo dpkg-query -l | grep coq *
You will get with coq package name, version, architecture and description in a table
| Distro | Debian 9 stretch |
| Section | Mathematics |
| Package | coq |
| Version | 8.5-2+b1 |
| Description | proof assistant for higher-order logic (toplevel and compiler) |
| Sub Section | Math |