Discussion: Whether to use auto for iterators

[stephengtuggy]

          I'm fine with type inference where it is trivial. Example from other languages is something like

let someString = String('blah blah')

However, I'm less comfortable with replacing std::list::iterator with auto. I prefer to clearly see my C++ abominations.

Originally posted by @royfalk in #789 (comment)

[BenjamenMeyer]

In general, I highly prefer being specific with types - even return types - and really don't like auto as a type.
However, one of the few cases where I find it okay is with dealing with the iterator types of objects since:

std::vector<someObject>::iterator

can be quite bother some to type out regularly. So using auto in that case can be acceptable, but I wouldn't say that's necessarily true of every case it might be used.

For example, looping over an iterable should generally be done in a relatively short block so the type should be generally evident especially since you're iterating over it so auto would likely be used . The following is a good use case:

for (auto entry =  myIterableType.begin();  entry != myIterableType.end(); ++entry) {
    ...
    // do something
   ...
}

However, if you're randomly accessing the iterator where it's going to get handed around or manipulated outside of a loop then auto really isn't good and type enforcement should be more strict.

iterableType::iterator instanceObject = myIterableType.begin();
// do something outside of the loop.
...

Make sense?

[stephengtuggy]

Makes sense to me.