Thread: The code from the internet, it's nonsense, or is it?

Code:

#include <algorithm>
#include <iostream>
#include <list>
#include <string>

int main()
{
    int array[ 17 ] = { 7,3,3,7,6,5,8,7,2,1,3,8,7,3,8,4,3 };

    int elem = array[ 9 ];
    int *found_it;

    found_it = std::find( &array[0], &array[17], elem );

    // печатается: поиск первого вхождения 1 найдено!

    std::cout <<  "поиск первого вхождения "
         << elem <<"\t"
         <<  ( found_it ? "найдено!\n" : "не найдено!\n" );

     std::string beethoven[] = {
        "Sonata31", "Sonata32", "Quartet14", "Quartet15",
       "Archduke", "Symphony7" };

    std::string s_elem( beethoven[ 1 ] );

     std::list< std::string, std::allocator > slist( beethoven, beethoven+6 );
    std::list< std::string, std::allocator >::iterator iter;

    iter = find( slist.begin(), slist.end(), s_elem );

    // печатается: поиск первого вхождения Sonata32 найдено!

    std::cout <<  "поиск первого вхождения "
         <<  s_elem <<  "\t"
         <<  ( found_it ? "найдено!\n" : "не найдено!\n" );
}

The code from the internet, it's nonsense, or is it?

std::list< std::string, std::allocator > slist( beethoven, beethoven+6 );&&????????

Have you tried compiling it? The code looks to be using a particular constructor that takes two iterators, in this case the range from the first element, to the 6th of the beethoven array.

It should be

Code:

std::list< std::string, std::allocator<std::string> >

although the std::allocator<std::string> part is not necessary since that's what it would default to.

Maybe the <std::string> part was hidden because it was interpreted as a tag by the webpage. Do you have the link?

Which part of that line of code looks like nonsense?

In the STL, containers like `std::list` are called "allocator-aware" which means that you can swap out the class that the container uses for its allocation routines.

You can also create most containers from a pair of iterators and all pointers are iterators (they're technically RandomAccessIterators which are all InputIterators from the STL's point of view). Keep in mind that in C/C++, array objects will implicitly decay into a pointer type.

Thank you, thank you very much!

I'm still just learning. So a lot of code seems strange or unusual, incomprehensible to me.

Well, the general advice around using namespaces explicitly is because C++ has overloading so one function or operator may have multiple definitions scattered through the codebase, including separate namespaces. So there's a danger in refactoring that you'll wind up calling something you didn't mean to. As long as the compiler can find a suitable definition, it'll call whatever it's found.

The STL is also full of somewhat generic and common names so the danger increases even more. You just gotta be careful, is all. Make sure you also never have a `using` statement in something like a header file as well.