[aktiur]

Your function in the tail recursion optimization exemple is actually not tail recursive. Factorial needs an accumulator parameter to get that tail call.

[agumonkey]

Maybe the decorator rewrites the AST. I've seen this before.

[santialbo]

It does, when the function is actually tco optimizable. The example is not. On the docs however it's correct http://coconut.readthedocs.io/en/master/DOCS.html#recursive