将整数连接到const char *字符串

Question

I have a few files named like so: file1 , file2 , file3 , etc.

I have a function:

load(const char *file)

which I would call like so load(file1) , load(file2) , etc.

I am trying do this a bit more dynamically, based on the number of files imported.

So if I have more than 1 file do something like this:

if (NUM_OF_FILES > 1) {
    for (int i = 2; i <= NUM_OF_FILES; i++) {
        load("file" + i);
    }
}

However, this is not working.

Is there a way of doing this?

Answer 1

The type of a string literal like "file" is char const[N] (with a suitable N ) whic happily decays into a char const* upon the first chance it gets. Although there is no addition defeined between T[N] and int , there is an addition defined between char const* and int : it adds the int to the pointer. That isn't quite what you want.

You probably want to convert the int into a suitable std::string , combine this with the string literal you got, and get a char const* from that:

load(("file" + std::to_string(i)).c_str());

Answer 2

It depends on what version of C++ you are using. If it's C++11, the solution will involve std::to_string . If it's an older version of C++, you can convert an integer to a string like this:

#include <sstream>

// ...

std::ostringstream converter;
converter << i; // i is an int
std::string s(convert.str());

Now, the load function takes a const char * . Is it your own function? Then consider changing it so that it takes a std::string const& instead, and you'll be able to pass the string directly. Otherwise, this is how can pass the string's contents to it:

load(s.c_str());