std::string::remove_copy() and std::string::remove_copy_if()

std::string::remove_copy() and std::string::remove_copy_if() are two functions in C++ that operate on std::string objects. They both create a new string object that is a copy of the original string with certain characters removed based on specific conditions.

std::string::remove_copy()

The std::string::remove_copy() function creates a new string object that is a copy of the original string with all instances of a specified character removed. The function takes two arguments:

• The character to remove
• The string to be copied

Here is an example of how to use std::string::remove_copy():

std::string str = "Hello, world!";
char ch = 'o';
std::string new_str = str.remove_copy(ch);
std::cout << new_str << std::endl; // Prints "Hell, wrld!"

In this example, the original string str is "Hello, world!". The remove_copy() function is called with the argument ch set to 'o'. This removes all instances of "o" from the original string and creates a new string object new_str with the value "Hell, wrld!".

std::string::remove_copy_if()

The std::string::remove_copy_if() function creates a new string object that is a copy of the original string with all characters that meet a specific condition removed. The function takes two arguments:

• A function or functor that determines the condition for character removal
• The string to be copied

Here is an example of how to use std::string::remove_copy_if():

std::string str = "Hello, world!";
std::string new_str = str.remove_copy_if([](char ch) { return std::isupper(ch); });
std::cout << new_str << std::endl; // Prints "ello, world!"

In this example, the original string str is "Hello, world!". The remove_copy_if() function is called with a lambda function that removes all uppercase characters from the original string. The resulting new string object new_str has the value "ello, world!".

Overall, std::string::remove_copy() and std::string::remove_copy_if() can be useful for creating a new string object that is a modified version of an original string object.