字符串文字的C ++宏开始迭代器和结束迭代器

Question

I would like a macro like this

STR_ITERATORS("My string")

which produces

 pBegin, pEnd

You could use this to search a vector for example...

std::vector<char> str1;

std::search(str1.begin(), str1.end(), STR_ITERATORS("Look for this"));

Note that search takes two pairs of iterators, and the macro provides the second pair.

The macro can be written twice - once for normal chars, once for wide chars. It doesn't have to solve it all in one.

Note: I don't have the option to use the very latest compilers. (That makes it a bit boring doesn't it? :-)

Answer 1

In C++11, making your own search functions for this is easy.

template<class iter1, class iter2>
iter1 search(iter1 stackbegin, iter1 stackend, iter2 needlebegin, iter2 needleend)
{return std::search(stackbegin, stackend, needlebegin, needleend);}

template<class iter1, class needlecontainer>
iter1 search(iter1 stackbegin, iter1 stackend, const needlecontainer& needle)
{return std::search(stackbegin, stackend, std::begin(needle), std::end(needle));}

template<class stackcontainer, class needlecontainer>
decltype(std::begin(std::declval<stackcontainer>()))
search(const stackcontainer& stack, const needlecontainer& needle)
{return std::search(std::begin(stack), std::end(stack), std::begin(needle), std::end(needle));}

template<class stackcontainer, class needlecontainer>
decltype(std::begin(std::declval<stackcontainer>()))
search(stackcontainer& stack, const needlecontainer& needle)
{return std::search(std::begin(stack), std::end(stack), std::begin(needle), std::end(needle));}

and use them:

int main() {
    std::vector<char> str1;
    auto it = search(str1, "Look for this");
}

Proof of compilation: http://ideone.com/cO1rz (this version of gcc didn't have std::begin and std::end so I had to define them myself) and a C++03 version: http://ideone.com/gt1Do

If you really really really want a short macro, and you can guarantee that literals share the same space:

template<int N>
const char* end(const char(&s)[N]) {return s+N;}
#define STR_ITERATORS(X) X, end(X) //BE WARNED, HIGHLY UNSAFE, NOT PORTABLE

Answer 2

boost range provides overloads of algorithms to use ranges, and will automatically handle most STL-like collections. Specifically, strings can automatically convert to ranges as well. There are also the free functions begin and end.

Answer 3

template<int N>
int GetLengthOfLiteral(const wchar_t (&literal)[N]) { return N - 1; }

template<int N>
int GetLengthOfLiteral(const char (&literal)[N]) { return N - 1; }

#define LITERAL_ITERATORS(literal) (literal), ((literal) + GetLengthOfLiteral(literal)