Something akin to `std::optional` would have been great. These days, folks don't come to C++ from C and are not used to such under-the-hood tricks.
The committee decided that since the reference can't be null, therefore, we'll insert something into the map when someone "query" for a key. Perhaps two mistakes can make a right!! It is hard to make peace with it when you are used to a better alternative.
> These days, folks don't come to C++ from C and are not used to such under-the-hood tricks.
It's funny to see that, since I'm used to folks coming to C++ from C and bemoaning that C is a much more straightforward language which doesn't engage in such under-the-hood tricks.
> Something akin to `std::optional` would have been great.
So, map.find(), which returns an iterator, which you can use to check for "presence" by comparing against map.end()? (Or if you actually want to insert an element in your map, map.insert() or, as of C++17, map.try_emplace().)
Again, the standard library is weird and confusing unless you've spent years staring into the abyss, and there are many ways of doing subtly different things.
C++ does not have distinct operators for map[key] vs map[key] = val. Languages like JS and Python do, which is why they can offer different behavior in those scenarios (in the former case, JS returns a placeholder value; Python will raise an exception). But, that's only really relevant in the context of single-dimensional maps.
Autovivification is rather rare today, but back in the early 90s when the STL first came about (prior to C++'s design-by-committee process, fwiw), what language was around for inspiration? Perl. If you don't have autovivification (or something like it), then map[i][j][k] = val becomes much more painful to write. (Maybe this is intended.) Workarounds in, say, Python are either to use a defaultdict (which has this exact same behavior of inserting elements upon referencing a key that isn't present!) or to use a tuple as your key (which doesn't allow you to readily extract slices of your dict).
The committee decided that since the reference can't be null, therefore, we'll insert something into the map when someone "query" for a key. Perhaps two mistakes can make a right!! It is hard to make peace with it when you are used to a better alternative.