Compile-Time Optimizations for Separate Templates

1// MyTemplate.cpp
2#include "MyTemplate.h"
3
4template <typename T>
5void MyTemplate<T>::foo() {
6  // Implementation
7}
8
9// Explicit instantiations
10template class MyTemplate<int>;
11template class MyTemplate<double>;

1// MyTemplate.h
2template <typename T>
3class MyTemplate {
4  // Class definition
5};
6
7extern template class MyTemplate<int>;
8
9// MyTemplate.cpp
10template class MyTemplate<int>;

1// stdafx.h
2#include <vector>
3#include <string>
4#include <iostream>
5
6// Other commonly used headers
7// ...
8
9// Use this precompiled header in your .cpp files
10#include "stdafx.h"

1// Forward declare instead of including the full header
2template <typename T>
3class MyTemplate;
4
5void someFunction(MyTemplate<int>& obj);

1template <unsigned N>
2struct Factorial {
3  static constexpr unsigned value =
4    N * Factorial<N - 1>::value;
5};
6
7template <>
8struct Factorial<0> {
9  static constexpr unsigned value = 1;
10};
11
12// Usage
13constexpr unsigned result = Factorial<5>::value;

1#include <concepts>
2
3template <std::integral T>
4class MyIntegralTemplate {
5  // Implementation
6};

1// MyModule.ixx
2export module MyModule;
3
4export template <typename T>
5class MyTemplate {
6  // Implementation
7};

1// Usage
2import MyModule;

1template <typename T>
2class MyTemplate {
3 public:
4  void commonFunction() {
5    // Implement here, always instantiated
6  }
7
8  void rarelyUsedFunction();
9};

1// In a separate .cpp file
2template <typename T>
3void MyTemplate<T>::rarelyUsedFunction() {
4  // Implementation here, only instantiated when used
5}