Templates and C Generic Techniques in C and C++

What is Templates and C Generic Techniques?

Templates generate type-safe implementations from a pattern; C commonly uses macros, void pointers, or C11 _Generic.

Important points

Understand the C mechanism before comparing the C++ abstraction.
Use RAII and value semantics to express ownership.
Prefer type-safe compile-time abstractions over macros and casts.

C and C++ code examples

C

main.c

#include <stdio.h>

int max_int(int left, int right) {
    return left > right ? left : right;
}

double max_double(double left, double right) {
    return left > right ? left : right;
}

#define MAX(left, right) _Generic((left), \
    int: max_int, double: max_double)((left), (right))

int main(void) {
    printf("%d %.1f\n", MAX(3, 9), MAX(2.5, 7.0));
}

Result of running the code

9 7.0

C++

Run code →

main.cpp

#include <iostream>

template<class T>
T maximum(const T& left, const T& right) {
    return left > right ? left : right;
}

int main() {
    std::cout << maximum(3, 9) << ' '
              << maximum(2.5, 7.0) << '\n';
}

Result of running the code

9 7

C and C++ comparison

The C11 _Generic expression selects a typed function but requires listing supported types. A C++ function template works for every type satisfying its operations.

C

C uses naming conventions, callbacks, macros, and explicit context structures.

C++

Language features provide scoped, type-safe, and often zero-overhead abstractions.

Practice exercises

Run both versions, then modify them to observe the different language guarantees.

Write the C mechanism before the C++ abstraction.
Remove manual cleanup with RAII.
Check whether the abstraction adds allocations or virtual dispatch.

Practice with a challenge

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