blt-demo software package provides graphics extension library for Tcl/Tk - demos and examples, 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 blt-demo
blt-demo is installed in your system.
Make ensure the blt-demo package were installed using the commands given below,
$ sudo dpkg-query -l | grep blt-demo *
You will get with blt-demo package name, version, architecture and description in a table
| Distro | Debian 9 stretch |
| Section | Development |
| Package | blt-demo |
| Version | 2.5.3+dfsg-3 |
| Description | graphics extension library for Tcl/Tk - demos and examples |
| Sub Section | devel |