C++ Foundations·Modern C++ without the folklore

Templates and generic code

Templates let one algorithm work with many types without losing static checking.

Intermediate 14 min read Lesson 9 of 300 Challenge included

What you will be able to do

Make templates small and focused.
Use concepts or static_assert to document requirements.
Keep error messages readable by constraining early.

In plain English

A template is checked when it is instantiated. Concepts (C++20) make requirements explicit. Prefer standard algorithms and constrained templates; avoid clever template metaprogramming unless it removes real duplication.

templates.cppC++

#include <concepts>
#include <iostream>

template <std::integral T>
T clamp(T value, T low, T high) {
    if (value < low) return low;
    if (value > high) return high;
    return value;
}

int main() {
    std::cout << clamp(120, 0, 100) << "\n";
}

Your turn

Clamp a value

Medium

Write a function template clamp(value, low, high) that constrains T to an integral type.

CPP · starter

template <typename T>
T clamp(T value, T low, T high) { return value; }

Check your understanding before moving on.

Knowledge checkQuestion 1

What does a concept do in C++20?

Select an answer to continue

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