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  1. #1
    John E is offline Elite Member Power Poster
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    [RESOLVED] Checking characters in Glib::ustring

    Can anyone give my some code for iterating through a Glib::ustring and obtaining the characters one-by-one? I assumed Glib::ustring_Iterator would help me but no matter what I do with it I can't make anything that'll compile. It's either a bit more complex than I thought or I'm missing something blindingly simple.
    "A problem well stated is a problem half solved. - Charles F. Kettering

  2. #2
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    Re: Checking characters in Glib::ustring

    Hi John E
    I'm not sure if this is what you're looking for but this compiles okay with GCC 4.4.1
    Code:
    #include <iostream>
    #include <iterator>
    #include <algorithm>
    #include <glibmm.h>
    
    int main()
    {
        Glib::ustring cow("cow");
        std::copy(cow.begin(), cow.end(), std::ostream_iterator<gchar>(std::cout, " "));
    }
    I haven't used Glib, but a quick look at the documentation, I suppose you could do pretty much the same thing with the ustring as you would with std::string

  3. #3
    John E is offline Elite Member Power Poster
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    Re: Checking characters in Glib::ustring

    Thanks for the suggestion. Yes, it does work if I copy the string to a buffer but that kinda defeats the object of using the template library. What I don't understand is why I can't do this:-

    Code:
    Glib::ustring cow("cow");
    Glib::ustring_Iterator<gunichar> iter = cow.begin();
    Obviously I've misunderstood the syntax because the above code doesn't compile. The problem is that I've tried numerous variants on the same kind of theme but I can't get anything along those lines to compile. Unfortunately, I can't find any examples anywhere either....
    "A problem well stated is a problem half solved. - Charles F. Kettering

  4. #4
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    Re: Checking characters in Glib::ustring

    Code:
    Glib::ustring cow("cow");
    Glib::ustring_Iterator<gunichar> iter = cow.begin();
    Why do you need to state the template argument?
    Code:
    Glib::ustring cow("cow");
    Glib::ustring_Iterator iter = cow.begin();
    I would have expected this to be the correct way to do this.

    Regards,

    Paul McKenzie

  5. #5
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    Re: Checking characters in Glib::ustring

    I see 2 overloads for ustring_Iterator
    Code:
      inline ustring_Iterator();
      inline ustring_Iterator(const ustring_Iterator<std::string::iterator>& other);
    where gunichar is unsigned int and is the ustring::value_type
    so i think the code should be
    Code:
        Glib::ustring_Iterator<std::string::const_iterator> iter = cow.begin();
    Edit:
    May I ask, why you're not using ustring::iterator?

    Edit:
    Wait, I posted the wrong code
    Code:
      typedef ustring_Iterator<std::string::iterator>       iterator;
      typedef ustring_Iterator<std::string::const_iterator> const_iterator;
    as you can see ustring_Iterator takes string's iterators,
    so I suppose passing gunichar to string::iterator which expects a single byte char type won't work.
    Last edited by potatoCode; February 15th, 2010 at 12:41 AM.

  6. #6
    John E is offline Elite Member Power Poster
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    Re: Checking characters in Glib::ustring

    Quote Originally Posted by Paul McKenzie View Post
    Why do you need to state the template argument?
    Code:
    Glib::ustring cow("cow");
    Glib::ustring_Iterator iter = cow.begin();
    I would have expected this to be the correct way to do this.
    Thanks Paul but that's one of the variations I tried. However, it gave me this compiler error:-

    error C2955: 'Glib::ustring_Iterator' : use of class template requires template argument list


    Quote Originally Posted by potatoCode View Post
    Edit:
    May I ask, why you're not using ustring::iterator?
    Oops.... When I found Glib::ustring_Iterator it didn't occur to me to look for anything else but Glib::ustring::iterator is indeed the solution to my problem. I had a feeling that I must have missed something obvious!
    "A problem well stated is a problem half solved. - Charles F. Kettering

  7. #7
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    Re: Checking characters in Glib::ustring

    I had a feeling that I must have missed something obvious!
    John E, I might still be a newbie here, but I know exactly how that feels
    Last edited by potatoCode; February 15th, 2010 at 11:58 PM. Reason: added the word

  8. #8
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    Re: Checking characters in Glib::ustring

    Quote Originally Posted by John E View Post
    Oops.... When I found Glib::ustring_Iterator it didn't occur to me to look for anything else but Glib::ustring::iterator is indeed the solution to my problem. I had a feeling that I must have missed something obvious!
    Now I see why it seemed strange that the iterator didn't automatically know the type it's iterating over without specifying the template argument.

    The actual type is ustring::iterator. When I first looked at it, this is what I thought a ustring_iterator meant, but obviously, they are two different things.

    Regards,

    Paul McKenzie

  9. #9
    John E is offline Elite Member Power Poster
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    Re: Checking characters in Glib::ustring

    Yes, I suspect the fact that "Iterator" uses a capital 'I' (Glib::ustring_Iterator) was possibly intended to give some kind of clue that it isn't the same thing as Glib::ustring::iterator but I must admit, that subtlety was lost on me..!
    "A problem well stated is a problem half solved. - Charles F. Kettering

  10. #10
    John E is offline Elite Member Power Poster
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    Re: Checking characters in Glib::ustring

    Sorry to resurrect an ancient thread but this is vaguely connected....

    Code:
    Glib::ustring infin = _("\u221e"); // Should display an infinity sign
    The above code displays an infinity sign when compiled with gcc but for me with MSVC it seems to produce a question mark. I've tried VS2019 and also a much earlier version of MSVC (VC8).

    And yet according to my Windows Character Map, the hex character 221e is indeed an infinity sign.

    Just wondering if anyone else could try it? The question mark is visible, even in the Debugger window.

    [Edit...] I've a feeling that locale_from_utf8() should be helping here - e.g.

    Code:
    Glib::ustring infin = Glib::locale_from_utf8 ("\u221e");
    or maybe this....

    Code:
    std::string infin = Glib::locale_from_utf8 ("\u221e");
    but they both still give me a question mark for some reason... What am I missing
    Last edited by John E; July 21st, 2021 at 12:18 PM.
    "A problem well stated is a problem half solved. - Charles F. Kettering

  11. #11
    John E is offline Elite Member Power Poster
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    Re: Checking characters in Glib::ustring

    Quote Originally Posted by John E View Post
    or maybe this....

    Code:
    std::string infin = Glib::locale_from_utf8 ("\u221e");
    but they both still give me a question mark for some reason... What am I missing
    Something just occurred to me... Glib::locale_from_utf8() returns std::string - so maybe std::string only supports simple strings - i.e. strings which can be represented by single characters?

    And maybe the infinity sign can't be represented by a single char?
    "A problem well stated is a problem half solved. - Charles F. Kettering

  12. #12
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    Re: Checking characters in Glib::ustring

    Is it possible to convert it to std::wstring?
    Victor Nijegorodov

  13. #13
    John E is offline Elite Member Power Poster
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    Re: Checking characters in Glib::ustring

    Thanks Victor - this won't compile (gives me error C2440: 'initializing': cannot convert from 'Glib::ustring' to 'std::basic_string<wchar_t,std::char_traits<wchar_t>,std::allocator<wchar_t>>')

    Code:
    Glib::ustring infin = _("\u221e");
    std::wstring strTest = infin;
    but interestingly, this initialises correctly:-

    Code:
    std::wstring strTest = L"\u221e";
    So my next thought was to try this - except that it also gives C2440

    Code:
    std::wstring strTest = L"\u221e";
    Glib::ustring infin = strTest; // <--- C2440
    "A problem well stated is a problem half solved. - Charles F. Kettering

  14. #14
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    Re: Checking characters in Glib::ustring

    Hi John,
    I guess there should exist some functions in Glib to convert from UTF8 to UNICODE and vice versa. However, I never used this library and I don't have any documentation either.
    Victor Nijegorodov

  15. #15
    John E is offline Elite Member Power Poster
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    Re: Checking characters in Glib::ustring

    Good suggestion Victor. I found a function called g_utf16_to_utf8()

    Code:
    std::wstring infin = L"\u221e"; // Initialises to an infinity sign
    gchar* winCompatibleInfin = g_utf16_to_utf8 (reinterpret_cast<gunichar2 const*>(infin.c_str()), -1, NULL, NULL, NULL);
    winCompatibleInfin looks a bit weird when viewed in the debugger - but in the finished app it does print out an infinity sign!!
    "A problem well stated is a problem half solved. - Charles F. Kettering

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