why not use enums for tree_criterion, parametric_method, selection_criterion?

[slayoo]

No description provided.

[tvatter]

That's a good idea.

The only "con" argument that I see is that it is more cumbersome to write e.g. tree_criterion::tau than just "tau".

[tnagler]

Agree. The "pro" argument is that the code expresses more clearly what "tau" is ;)

[tvatter]

Definitely, and using enums also prevents the need for error messages, but both pros were kind of obvious, hence the quotes for "con" :)

All in favor say aye.

[tnagler]

Let's do it!