An Actually Helpful Character Type

As we have seen last time, having char8_t is not terribly useful. But we discovered that another character type is actually quite useful.

In the last post, I recommended not to commit to a single string encoding for a given program but instead use the encoding native to the domain the string is used in. This avoids conversions which may cause problems for special cases, like Windows allowing file names containing invalid UTF-16.

Now, there are situations where you want to use the same string in different domains, for example a file name in both UI and the OS file API. We found that quite often, these strings contain solely ASCII characters, in particular when dealing with string constants: file names, query parameters, etc. In these cases, conversion is trivial, cheap and, very importantly, works character by character, no need to supply a complete string.

We introduced a character type for this purpose, tc::char_ascii, which documents and asserts to only contain ASCII and converts implicitly to all character types, without triggering a narrowing compiler warning. It’s part of the think-cell library, so try it out!