adding method to STL class

This is a discussion on adding method to STL class within the C++ Programming forums, part of the General Programming Boards category; Can I do that? I just wrote a "tokenize string" function: Code: vector<string> tokenize(string &str, string tokens); and then thot, ...

  1. #1
    spurious conceit MK27's Avatar
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    adding method to STL class

    Can I do that? I just wrote a "tokenize string" function:
    Code:
    vector<string> tokenize(string &str, string tokens);
    and then thot, well, why not do this:
    Code:
    vector<string> string::tokenize(string tokens);
    However, I get "error: too few template-parameter-lists" for that line...
    Last edited by MK27; 03-27-2010 at 10:04 AM.
    C programming resources:
    GNU C Function and Macro Index -- glibc reference manual
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    Current ISO draft standard
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  2. #2
    and the Hat of Guessing tabstop's Avatar
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    To add members to a class, well, you need source for the class (because that name has to appear in the definition). And then, of course, almost by definition, you are no longer in std::string, but MK27::string.

    I've never tried to inherit from a STL class (which seems like the next most obvious choice), but I remember hearing that it usually fails horribly since the STL wasn't really designed for that sort of thing.

    (ETA: And of course, since string is a template class with (at least) three templated arguments (i.e., string<charT, traits, allocator>) you would have to have that in your definition as well.)
    Last edited by tabstop; 03-27-2010 at 10:12 AM.

  3. #3
    The larch
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    Free functions are they way to go if you want to extend the interface of existing classes.
    I might be wrong.

    Thank you, anon. You sure know how to recognize different types of trees from quite a long way away.
    Quoted more than 1000 times (I hope).

  4. #4
    spurious conceit MK27's Avatar
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    Probably not worth the bother then.

    Quote Originally Posted by tabstop View Post
    I've never tried to inherit from a STL class (which seems like the next most obvious choice), but I remember hearing that it usually fails horribly since the STL wasn't really designed for that sort of thing.
    I believe the caveat has to do STL classes not having virtual functions, so:
    Code:
    string *ptr = new myDerivedClass(...
    will foul up.
    C programming resources:
    GNU C Function and Macro Index -- glibc reference manual
    The C Book -- nice online learner guide
    Current ISO draft standard
    CCAN -- new CPAN like open source library repository
    3 (different) GNU debugger tutorials: #1 -- #2 -- #3
    cpwiki -- our wiki on sourceforge

  5. #5
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    How about writing a wrapper class around it?

  6. #6
    C++ Witch laserlight's Avatar
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    There is no point in writing a wrapper class; writing a free function like what you did will do.
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