std::string s1 {"Modern C++", 3} vs std::string s1 {str, 3}

Solution 1:

From:

https://en.cppreference.com/w/cpp/string/basic_string/basic_string

std::string s1 {"Modern C++", 3};

Uses the following constructor:

basic_string( const CharT* s,
          size_type count,
          const Allocator& alloc = Allocator() );

So takes 3 chars to get Mod.

std::string s2 {str, 3};

will use the following constructor:

basic_string( const basic_string& other,
          size_type pos,
          const Allocator& alloc = Allocator() );

So taking the string from position 3 onwards giving : ern C++.

Solution 2:

One is calling string(char const*, count), the other string(string const&, pos).

One gets the first 3 characters from a buffer, the other all the characters after the 3rd one.

This is because C++ has raw character buffers and std strings. "this is not a std::string". "this is a std string"s, std::string so_is="this";.

std::string is more than 30 years old, and it was added to the C++ language without sufficient care (unlike the STL, which went through more iterations before being added).

Its interface is honestly too rich, and you can run into stuff like this; multiple overloads that lead to confusing results.

std::string s1 {"Modern C++", 3} vs std::string s1 {str, 3}

Solution 1:

Solution 2:

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