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Comment by cherryteastain | Hacker News Reader

Wish they returned std::expected<T, std::errc> instead of the weird from_chars_result struct

std::expected is new in C++23, std::from_chars was introduces in C++17. Obviously, 2023 features were not available in 2017. Changing the return type now would break everybody's code, with very little benefit, you can easily wrap std::from_chars.

If returning std::expected makes more sense, why not make it the primary signature and create a wrapper to maintain compatibility with old code?

Then you would have to use 2 names: the primary name and the wrapper name. What would they be? Using 2 names wastes more of the namespace, and will confuse people. If the wrapper name isn't from_chars, then people's code will break when upgrading.

Oh right. A different return type isn't enough to differentiate one function from another.

They could add an overload like std::expected<T, std::errc> from_chars(std::string_view). That way, since the input arguments are different, there'd be no issues about overload resolution.

But overloads providing slightly different interfaces are a bane to generic programming.

Overloads are already confusing, if they can't be used generically there is really no point in reusing the name.

Having an inconsistent, special case way of doing something in the name of backwards compatibility is the defining characteristic of C++.

It's a tradeoff.

For example: With Python Python breaking changes are more common, and everyone complains about how much they have to go and fix every time something changes.

Damned if you do, damned if you don't. Either have good backwards compatibility but sloppy older parts of the language - or have a 'cleaner' overall language at the cost of crushing the community every time you want to change anything.

I'm fully aware, just pointing out that C++ is particularly afflicted with backward compatibility issues; far more than other languages.

"The Design and Evolution of C++" gives the impression that even back in the 80s, major concessions were being made in the name of compatibility. At that time it was with C; now it's with previous versions of C++.

from_chars_result closely matches the strtol line of functions we've had for decades. Not returning the end position would be weird here!

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