erase any non numeric characters from an input

[eggs831]

How do i erase a certain type of character from a string input?

Thanks

[xismn]

#include <iostream>
#include <string>
#include <algorithm>

auto predicate_is_not_digit = [](const char& character) {
	return !(::isdigit(character));
};

int main() {

	std::string string = "a1b2c3d4,./-HELLOWORLD";

	std::cout << "String before purging non-digit characters:\t" << string << std::endl;

	string.erase(std::remove_if(string.begin(), string.end(), predicate_is_not_digit), string.end());

	std::cout << "String after purging non-digit characters:\t" << string << std::endl;

	return 0;
}