Basic things I need to know

This is a discussion on Basic things I need to know within the C++ Programming forums, part of the General Programming Boards category; Originally Posted by maxorator zx-1 , the second one works with 16bit, 32bit and 64bit Unicode versions too. Nope. That'd ...

  1. #16
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    Quote Originally Posted by maxorator
    zx-1, the second one works with 16bit, 32bit and 64bit Unicode versions too.
    Nope. That'd be with sizeof(wchar_t), assuming there's a difference between wide and and narrow chars.
    Last edited by zx-1; 10-09-2006 at 06:23 AM.
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  2. #17
    Reverse Engineer maxorator's Avatar
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    I see no differences then because sizeof(char) is always 1 byte.
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  3. #18
    Reverse Engineer maxorator's Avatar
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    Quote Originally Posted by Queatrix
    So much for inactive.
    Actually it was midnight. I just thought I'd look if there's something interesting here before I went to sleep.
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  4. #19
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    Quote Originally Posted by maxorator
    I see no differences then because sizeof(char) is always 1 byte.
    That's 95% correct. There is a difference, albeit a somewhat esoteric one.
    It was really kind of a trick question. :-)
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  5. #20
    Reverse Engineer maxorator's Avatar
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    Hmm, you can define char to be something else?
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  6. #21
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    No. Answer:
    8192 is the same as (int)8192.
    8192 * sizeof(char) is the same as (size_t)8192.
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  7. #22
    C++ Witch laserlight's Avatar
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    I assert that porting legacy code is the only valid reason for having "using" in your code. It decreases readability; putting std:: in front of everything makes it far more clear what's going on.
    I think that this is another valid use of "using":
    Code:
    void ClassName::swap(ClassName& x) {
        using std::swap;
        swap(member1, x.member1);
        swap(member2, x.member2);
    }
    At the initial point when the code was written, it is possible that the types of member1 and member2 do not yet have their own (presumably optimised) swap functions. As such, the standard swap algorithm would be used. At some later point, this might change, and thus a re-compile should have ClassName::swap pick up the optimisations automatically.

    Here is another valid use of "using":
    Code:
    #include <iostream>
    
    class Base {
    public:
        void memberFunction() {
            std::cout << "Base::memberFunction()" << std::endl;
        }
    
        virtual void memberFunction(int num) {
            std::cout << "Base::memberFunction(" << num << ")" << std::endl;
        }
    };
    
    class Derived : public Base {
    public:
        using Base::memberFunction;
        virtual void memberFunction(int num) {
            std::cout << "Derived::memberFunction(" << num << ")" << std::endl;
        }
    };
    
    int main() {
        Derived x;
        x.memberFunction();
    }
    If the "using Base::memberFunction;" was commented out, there would be a compile error, since Derived::memberFunction(int) hides the name "memberFunction" in the Base class' scope. As such, a call to Base::memberFunction() from x would be invalid.
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  8. #23
    Cat without Hat CornedBee's Avatar
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    I think Cat was referring to the using statement, not the using declaration. But far be it from me to place words in his mouth

    zx-1: it actually took me two looks on your code to find the difference. Very nice example.

    maxorator: no, but you need to learn good design.
    All the buzzt!
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  9. #24
    Reverse Engineer maxorator's Avatar
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    Well, I see the difference too, one of them is shorter than the other one.
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  10. #25
    Frequently Quite Prolix dwks's Avatar
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    4. In C, it is in the <string.h> library.
    Look again.
    6. Do you mean kind of overload the template with a template function that has parameters types specified, so when those types are used in the function, that function template is used?
    I mean that you can have a generic template class, like vector<>, but also a specialized version, such as vector<bool>, which has a slightly different behaviour.
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    What should you do if you detect an error while in a constructor? What about a destructor? Why is auto_ptr<> not appropriate for holding pointers that will be stored in standard containers? What is a good alternative? What is the airspeed velocity of an unladen swallow? Is that airspeed sufficient to carry a coconut?
    The crows maintain that a single crow could destroy the heavens. Doubtless this is so. But it proves nothing against the heavens, for the heavens signify simply: the impossibility of crows.

  12. #27
    Reverse Engineer maxorator's Avatar
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    Look again.
    Oh, sorry, accidentally compiled it as C++, stdio.h of course.
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  13. #28
    Registered User whiteflags's Avatar
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    The question: What header file is tolower() in?
    Quote Originally Posted by maxorator
    [...] stdio.h of course.
    Wrong! Better start using your grepping power.
    Last edited by whiteflags; 10-10-2006 at 12:38 PM. Reason: Needed more Luthor

  14. #29
    Frequently Quite Prolix dwks's Avatar
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    Third time lucky.
    Better start using your grepping power.
    Or man tolower or google("site:cppreference.com tolower") or countless other ways.
    dwk

    Seek and ye shall find. quaere et invenies.

    "Simplicity does not precede complexity, but follows it." -- Alan Perlis
    "Testing can only prove the presence of bugs, not their absence." -- Edsger Dijkstra
    "The only real mistake is the one from which we learn nothing." -- John Powell


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  15. #30
    Reverse Engineer maxorator's Avatar
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    What's the difference? Stdio.h automatically includes ctype.h.
    What do you mean by "man"?
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