从 std::vector 初始化 std::string<unsigned char> 导致错误

Question

In C++ we can create a vector from another vector via
std::vector<unsigned char> tmp_1 { &some_vector[i] , &some_vector[j] };

Question : Is there any way to do the same for std::string ?
Something like:

std::string tmp2 { &some_vector[i] , &some_vector[j] };

Attempts to use constructor from documentation always return error;

Note: *some_vector is the vector of unsigned chars

UPD : Found answer: had typo so tried to access [-1] element.

Answer 1

This:

std::string tmp2 { &some_vector[i] , &some_vector[j] };

should work for std::vector but I would prefer more readable and safer solution:

std::string tmp2 { std::next( some_container, i ) , std::next( some_container.begin(), j ) };

which should work on any container with type, that can be convertible to char . For example if you or somebody else later would decide to replace std::vector<char> to std::deque<char> for whatever reason, your program will suddenly and what is more dangerous quietly start to be unpredictable with &container[i] .

Answer 2

std::string has several constructors , some of which can be used to construct the string from a std::vector , eg:

// using a char* pointer and a size...
std::string tmp2( reinterpret_cast<char*>(&some_vector[i]), j-i );

// using char* pointers as iterators...
std::string tmp2( &some_vector[i], &some_vector[j] );

// using vector iterators...
std::string tmp2( some_vector.begin()+i, some_vector.begin()+j );

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