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Master Modern C++

Function and Class Templates

Explore how function and class templates allow you to write generic, reusable C++ code that works with any data type. Understand template syntax, instantiation, and benefits such as type safety, code reuse, and zero runtime overhead to build efficient and maintainable programs.

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Up until now, we have defined functions and classes that operate on specific types, like int or double. But what happens when we need the exact same logic for different data types? Imagine writing three versions of a swap function: one for integers, one for floats, and one for strings. This violates the "Don't Repeat Yourself" (DRY) principle and creates a maintenance nightmare.

The problem of duplication

Static typing is a core strength of C++, but it can sometimes feel rigid. Imagine we need a function to find the larger of two values. Without templates, we might write:

C++
int get_max(int a, int b) {
    if (a>=b)
        return a;
    return b;
}
double get_max(double a, double b) {
    if (a>=b)
        return a;
    return b;
}

The logic is identical; only the types differ. If we want to support float or long, we must copy-paste this code again. This duplication invites bugs: if we change the logic in one version, we might forget to update the others. C++ solves this problem with templates.

Function templates

Templates allow us to write a single "blueprint" that the compiler uses to generate the correct code for any type we need. This mechanism powers the entire STL and allows us to write code that is both generic and type-safe.

C++ ...