C++:
Interpolating a string
How to:
C++ doesn’t have built-in string interpolation like some other languages. You often use std::ostringstream, std::format (from C++20), or printf-style formatting.
With std::ostringstream:
#include <sstream>
#include <iostream>
int main() {
std::ostringstream message;
int age = 30;
message << "Hello, I am " << age << " years old.";
std::cout << message.str() << std::endl; // "Hello, I am 30 years old."
}With std::format (C++20):
#include <format>
#include <iostream>
int main() {
int age = 30;
std::string message = std::format("Hello, I am {} years old.", age);
std::cout << message << std::endl; // "Hello, I am 30 years old."
}Deep Dive
Before C++20, we concatenated strings with streams or sprintf, which was clunky. With the advent of std::format, we’re catching up to modern languages like Python with their f-strings.
std::ostringstream: This gives us a stream-like way to build up strings. It’s versatile but not the most concise. It’s been the go-to for years because it’s safe and easy to use.
std::format: Introduced in C++20, it offers Python-like formatting. It’s more readable and efficient than stream concatenation but requires newer compilers.
Alternatives exist like Boost.Format or using string concatenation, but they aren’t as clean or may incur overhead.
String interpolation is sugar, but it’s sweet. It simplifies code and avoids the performance hit of repeatedly appending strings.