How do I install the Ada compiler?
Solution 1:
Ubuntu comes with the Ada compiler GNAT (package gnat) as part of the GNU Compiler Collection and the GNAT Programming Studio (package gnat-gps), an IDE for GNAT.
See AdaCore documentation page for documentation.
Solution 2:
Looking in the terminal's history on a Ubuntu 10.04 VM here, I have sudo apt-get install gnat-4.4 and it appears to have worked at the first time. Perhaps the GNAT version is not even needed there.