libarmadillo-dev software package provides streamlined C++ linear algebra library - Headers, you can install in your Debian 8 (Jessie) by running the commands given below on the terminal,
$ sudo apt-get update $ sudo apt-get install libarmadillo-dev
libarmadillo-dev is installed in your system.
Make ensure the libarmadillo-dev package were installed using the commands given below,
$ sudo dpkg-query -l | grep libarmadillo-dev *
You will get with libarmadillo-dev package name, version, architecture and description in a table
| Distro | Debian 8 jessie |
| Section | Library development |
| Package | libarmadillo-dev |
| Version | 1:4.450.2+dfsg-1 |
| Description | streamlined C++ linear algebra library - Headers |
| Sub Section | Libdevel |