alex software package provides lexical analyser generator for Haskell, you can install in your Ubuntu 16.04 LTS (Xenial Xerus) by running the commands given below on the terminal,
$ sudo apt-get update $ sudo apt-get install alex
alex is installed in your system.
Make ensure the alex package were installed using the commands given below,
$ sudo dpkg-query -l | grep alex *
You will get with alex package name, version, architecture and description in a table
| Distro | Ubuntu 16 04 lts xenial xerus |
| Section | Development |
| Package | alex |
| Version | 3.1.6-1 |
| Description | lexical analyser generator for Haskell |
| Sub Section | Devel |