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For ascii in C++ isn't there std::tolower / std::toupper? If you're not dealing with unsigned char types there isn't a simple case conversion function, but that

For ascii in C++ isn't there std::tolower / std::toupper? If you're not dealing with unsigned char types there isn't a simple case conversion function, but that's for a good reason as the article lays out.

fluoridation 2y ago
Those functions take and return single characters. What's missing is functions that operate on strings. You can use them in combination with std::transform(), but as the article points out, even if you're just dealing with ASCII you can easily do it wrong. I've been using C++ for over 20 years and I didn't know tolower() and toupper() were non-addressable. There's really no excuse for the library not having simple case conversion functions that operate on strings in-place.
- theelous3 2y ago
  > There's really no excuse for the library not having simple case conversion functions that operate on strings in-place. Could not agree more. Any time I touch a C I want to scoop my brain out of my ear. So many simple unbelievably common operations have fifty "best" ways to do them, when they should have one happy path 99% of usecases require baked in. Nobody should ever have to seriously consider something as ridiculous as "is tolower addressable?".
- squeaky-clean 2y ago
  std::transform() seems like overkill when you can just iterate over the string and modify it in place. And in my opinion, tranform is way less readable than seeing a loop over some array with a single operation inside. The article talks about wstrings for good reason. If you're converting narrow strings, you don't need to be this fancy. Just loop over the string and edit it in place. If you are operating on wide strings, there is no suitable single solution, partly because wstring is a terrible type. It's different widths on different platforms, and no string encoding format uses a generalized wsring, they have mandatory min/max character byte widths. So a wstring tells you nothing about the actual encoded string contents semantic representation. The C++ stdlib could include a fully unicode aware string type set, and surrounding library. But personally I think C++ isn't the kind of language to provide an opinionated stdlib module for such a complex task. And there's no way to implement such a module without being very opinionated about something.
  - fluoridation 2y ago
    I know I can simply iterate. The point is that it's a function that should be included, not that it's impossible without it. It's one of the most common string operations.
    - squeaky-clean 2y ago
      To me that feels like the JS community asking for left-pad or is-even in a module. Why have a dedicated function for 2 lines of code? And it's a huge footgun. There is no ascii type in C++. People will use the generalized tolower for UTF8 encoded in narrow strings and have issues. You could say the generalized tolower should support all the different width/encoding combinations and sort it out. But that's still highly opinionated as far as performance is concerned. Generalized string conversion is a very complex problem and you really cannot simplify it in a way that will satisfy most C++ users. Just use ICU or utf8cpp if you want to do string operations and don't care what's going on under the hood. But even then I can't recommend just 1 library, because no perfect 3rd party library exists. A perfect first party library definitely could not exist.
      - fluoridation 2y ago
        >Why have a dedicated function for 2 lines of code? Then why does std::max() exist? >People will use the generalized tolower for UTF8 encoded in narrow strings and have issues. tolower() and toupper() work correctly on UTF-8 strings, because UTF-8 was specifically designed so that non-ASCII characters were represented by sequences of purely non-ASCII bytes. >Generalized string conversion is a very complex Hence why people who say C++ should have a tolower() that operates on strings are not asking more complex Unicode support.
  - dwattttt 2y ago
    > The article talks about wstrings for good reason. If you're converting narrow strings, you don't need to be this fancy. Just loop over the string and edit it in place. Since you mention narrow strings in the context of wstring, just to make sure... you can't convert a UTF-8 std::string character by character, in-place (in case that's what you meant). 7-bit ASCII code points are fine, but outside that it's not guaranteed that one UTF-8 byte converts into exactly one UTF-8 byte when converting case.
account42 2y ago
std::tolower / std::toupper are rubbish functions that can't do proper Unicode but still pull in the bloated locale machinery for what should be a simple conditional integer addition if all you care about is ASCII. Both have no valid use case and should be marked [[deprecated]] and erased from all teaching materials.
- deleted 2y ago
  [deleted]

fluoridation 2y ago

Those functions take and return single characters. What's missing is functions that operate on strings. You can use them in combination with std::transform(), but as the article points out, even if you're just dealing with ASCII you can easily do it wrong. I've been using C++ for over 20 years and I didn't know tolower() and toupper() were non-addressable. There's really no excuse for the library not having simple case conversion functions that operate on strings in-place.

theelous3 2y ago
> There's really no excuse for the library not having simple case conversion functions that operate on strings in-place. Could not agree more. Any time I touch a C I want to scoop my brain out of my ear. So many simple unbelievably common operations have fifty "best" ways to do them, when they should have one happy path 99% of usecases require baked in. Nobody should ever have to seriously consider something as ridiculous as "is tolower addressable?".
squeaky-clean 2y ago
std::transform() seems like overkill when you can just iterate over the string and modify it in place. And in my opinion, tranform is way less readable than seeing a loop over some array with a single operation inside. The article talks about wstrings for good reason. If you're converting narrow strings, you don't need to be this fancy. Just loop over the string and edit it in place. If you are operating on wide strings, there is no suitable single solution, partly because wstring is a terrible type. It's different widths on different platforms, and no string encoding format uses a generalized wsring, they have mandatory min/max character byte widths. So a wstring tells you nothing about the actual encoded string contents semantic representation. The C++ stdlib could include a fully unicode aware string type set, and surrounding library. But personally I think C++ isn't the kind of language to provide an opinionated stdlib module for such a complex task. And there's no way to implement such a module without being very opinionated about something.
- fluoridation 2y ago
  I know I can simply iterate. The point is that it's a function that should be included, not that it's impossible without it. It's one of the most common string operations.
  - squeaky-clean 2y ago
    To me that feels like the JS community asking for left-pad or is-even in a module. Why have a dedicated function for 2 lines of code? And it's a huge footgun. There is no ascii type in C++. People will use the generalized tolower for UTF8 encoded in narrow strings and have issues. You could say the generalized tolower should support all the different width/encoding combinations and sort it out. But that's still highly opinionated as far as performance is concerned. Generalized string conversion is a very complex problem and you really cannot simplify it in a way that will satisfy most C++ users. Just use ICU or utf8cpp if you want to do string operations and don't care what's going on under the hood. But even then I can't recommend just 1 library, because no perfect 3rd party library exists. A perfect first party library definitely could not exist.
    - fluoridation 2y ago
      >Why have a dedicated function for 2 lines of code? Then why does std::max() exist? >People will use the generalized tolower for UTF8 encoded in narrow strings and have issues. tolower() and toupper() work correctly on UTF-8 strings, because UTF-8 was specifically designed so that non-ASCII characters were represented by sequences of purely non-ASCII bytes. >Generalized string conversion is a very complex Hence why people who say C++ should have a tolower() that operates on strings are not asking more complex Unicode support.
- dwattttt 2y ago
  > The article talks about wstrings for good reason. If you're converting narrow strings, you don't need to be this fancy. Just loop over the string and edit it in place. Since you mention narrow strings in the context of wstring, just to make sure... you can't convert a UTF-8 std::string character by character, in-place (in case that's what you meant). 7-bit ASCII code points are fine, but outside that it's not guaranteed that one UTF-8 byte converts into exactly one UTF-8 byte when converting case.

account42 2y ago

std::tolower / std::toupper are rubbish functions that can't do proper Unicode but still pull in the bloated locale machinery for what should be a simple conditional integer addition if all you care about is ASCII. Both have no valid use case and should be marked [[deprecated]] and erased from all teaching materials.

deleted 2y ago
[deleted]