Prepare literalArguments for immutable builtin functions

[Marenz]

refs #8551

(incomplete)

[chriseth]

This PR contains unrelated commits.

[chriseth]

Please squash.

[Marenz]

Pushed update that addresses the feedback

[chriseth]

Can we create a helper for that? I think the i - 1 is really dangerous. Is there something like python's enumerate? Then we could use for (auto&& [i, arg]: enumerate(_funCall.arguments) | reversed)

[Marenz]

Yes absolutely. I wasn't happy with that either.

[chriseth]

http://reedbeta.com/blog/python-like-enumerate-in-cpp17/

[Marenz]

@christianparpart do you have a good idea how this could be done?

[ekpyron]

Maybe just

for (size_t i : boost::counting_range(0, _funCall.arguments.size()) | boost::adaptors::reversed)
{
  auto&& arg = _funCall.arguments[i];

? Or a very simple helper that returns boost::counting_range(0, _container.size())?

I could look into helpers that give you tuples of index and value that are robust against reversing - or even helpers that let you iterate two containers simultanously, so you could use auto&& [needsLiteralArgument, arg]: someWrapper(*needsLiteralArguments, _funCall.arguments) | boost::adaptors::reversed - that's possible, but it can get quite messy quickly :-).

[chriseth]

Did you see the link I posted above?

[ekpyron]

By the way: the solution in the link always creates a copy - a more sophisticated solution would use references for lvalues and move for rvalues (again part of the messy-ness ;-))

[leonardoalt]

I think it's fine as is. i - 1 is only used twice and the for line is very clear

[leonardoalt]

Maybe change i to something else though? i is also used below, might look confusing visually

[chriseth]

We have tons of other places in the code where an enumerate or "iterate two lists at the same time" would be very handy.

[chriseth]

Looks good apart from the enumerate feature. Should we merge this already as is?