starting with Pd-0.47 (no release yet, only git atm), the expr-object has become a built-in. so you probably need that version...

gfmadsr IOhannes

@Dave IOhannes is right (again). I use the latest commit on the master branch of the Git repository of Pure Data as a sub module. If you want to compile, the best is to pull the project from Git and to use the sub modules directly from Git. You'll have all the sources in the right place. PS: for Linux, you have dependencies. Everything is explained here: https://github.com/pierreguillot/Camomile/wiki/Compilation.