Range-For loop over a string adding a null or empty char at the end

user_17720234 0
Viewed 201

Here is a loop that goes through each character in "(Level:". It adds something to the end which is messing up the rest of my code.

#include <iostream>

int main() {
    std::cout << "Output:" << std::endl;
    for (char letter : "(Level:") {
        std::cout << "'" << letter << "'" << std::endl;
    }
    return 0;
}

Output:

'('
'L'
'e'
'v'
'e'
'l'
':'
''

I'm new to C++ and I don't understand what's happening.

c++
2 Answers

"(Level:" has type const char[8], and is equivalent to { '(', 'L', 'e', 'v', 'e', 'l', ':', '\0' }.

You can easily see this is the case by casting the letter to int before printing. Demo

This happens, because string literals (anything "...") are C-strings, which are zero terminated. If you want strings to have a size instead of a zero terminator, you can use a string_view literal:

#include <iostream>
#include <string_view>

using namespace std::literals::string_view_literals;

int main() {
    std::cout << "Output:" << std::endl;
    for (char letter : "(Level:"sv) {
        std::cout << "'" << letter << "' (" << static_cast<int>(letter) << ")\n";
    }
    return 0;
}

See the result

dionadar_656780

Cause the strings in C++ are all ended with '\0', we can't see it but it really exists. This hidden '\0' can marks the end of a string and can be read by your 'for' statement. You can add an 'if' statement in your 'for' statement to deal with '\0'.

#include <iostream>

int main() {
    std::cout << "Output:" << std::endl;
    for (char letter : "(Level:") {
        if (letter != '\0')
            std::cout << "'" << letter << "'" << std::endl;
    }
    return 0;
}
user_177212440
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