How Can I Restore the Original State of std::cout After Modifying Its Formatting?

Restoring the State of std::cout After Manipulation

In C , streams such as std::cout can be manipulated to alter their formatting and behavior. However, after such manipulations, restoring the stream's original state may be necessary.

Suppose you have the following code:

void printHex(std::ostream& x) {
    x << std::hex << 123;
}

int main() {
    std::cout << 100; // prints 100 base 10
    printHex(std::cout); // prints 123 in hex
    std::cout << 73; // problem! prints 73 in hex..
}

After calling printHex(), the state of std::cout has been altered to print integers in hexadecimal format. This causes a subsequent call to std::cout in the main function to also print in hex, potentially causing unexpected behavior.

To restore the original state of std::cout, we can use stream flags:

#include <iostream>

int main() {
    std::ios_base::fmtflags f(cout.flags());

    printHex(std::cout);

    cout.flags(f); // Restore original flags

    std::cout << 73; // prints 73 in decimal
}

In this example, the fmtflags object f stores the original stream flags of std::cout. After calling printHex(), we explicitly set the stream flags back to f's value using cout.flags(f). This ensures that std::cout's state is restored to its original settings.

By utilizing stream flags and restoring them appropriately, we can manipulate streams while maintaining control over their formatting behavior, avoiding unintended consequences like incorrect number formats in this case.

The above is the detailed content of How Can I Restore the Original State of std::cout After Modifying Its Formatting?. For more information, please follow other related articles on the PHP Chinese website!