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The All-in-One Guide to C++20

String prefix and suffix checking

Explore how to use C++20's new member functions starts_with and ends_with to check string prefixes and suffixes effectively. Understand their usage with std::string, std::string_view, and char inputs. This lesson helps you write more intuitive and readable container operations using modern C++ features.

We'll cover the following...

std::string gets new member functions starts_with and ends_with. They allow you to check if a std::string starts or ends with a specified substring.

C++
#include <iostream>
#include <string_view>
#include <string>
 
template <typename PrefixType>
void startsWith(const std::string& str, PrefixType prefix) {
    std::cout << "            starts with " << prefix << ": " <<
        str.starts_with(prefix) << '\n';
}
template <typename SuffixType>
void endsWith(const std::string& str, SuffixType suffix) {
    std::cout << "            ends with " << suffix << ": " <<
        str.ends_with(suffix) << '\n';
}
 
int main() {
    std::cout << std::endl;
    
    std::cout << std::boolalpha;
    
    std::string helloWorld("Hello World");
    
    std::cout << helloWorld << std::endl;
 
    startsWith(helloWorld, helloWorld);
 
    startsWith(helloWorld, std::string_view("Hello"));
 
    startsWith(helloWorld, 'H');
    
    std::cout << "\n\n"; 
    
    std::cout << helloWorld << std::endl;
 
    endsWith(helloWorld, helloWorld);
 
    endsWith(helloWorld, std::string_view("World"));
 
    endsWith(helloWorld, 'd');
}

Both member functions starts_with and ends_with are ...