lua print is very slow because it does not use streams but has to return a complete string.

[Broes De Cat]

instead of overriding to_string in lua, we should check whether we can override the action which prints to stream, so we do not have to generate the string completely first.

[Bart Bogaerts]

is this because of issue #313?

[Broes De Cat]

Not sure, but I do not expect the toString functions to be the only culprit.