An alternative to Boost is POCO (pocoproject.org).

POCO provides two variants:

1. The first variant makes a copy without altering the original string.
2. The second variant changes the original string in place.
   "In Place" versions always have "InPlace" in the name.
   

Both versions are demonstrated below:

#include "Poco/String.h"
using namespace Poco;

std::string hello("Stack Overflow!");

// Copies "STACK OVERFLOW!" into 'newString' without altering 'hello.'
std::string newString(toUpper(hello));

// Changes newString in-place to read "stack overflow!"
toLowerInPlace(newString);

An alternative to Boost is POCO (pocoproject.org).

POCO provides two variants:

1. The first variant makes a copy without altering the original string.
2. The second variant changes the original string in place.
   "In Place" versions always have "InPlace" in the name.
   

Both versions are demonstrated below:

#include "Poco/String.h"
using namespace Poco;

std::string hello("Stack Overflow!");
    
// Copies "STACK OVERFLOW!" into 'newString' without altering 'hello.'
std::string newString(toUpper(hello));
    
// Changes newString in-place to read "stack overflow!"
toLowerInPlace(newString);