C + + template meta-programming three: cyclic expansion

2.2Loop unrolling Looping expansion

The previous enum section describes the combination with the template, which throws a magical effect on the compiler recursion. The template itself can achieve recursive results without the need for enum mates.

Test template recursive for loop unrolling    cout << ' test 2:template recursive for Loop unrolling ' << E NDL;    for (size_t i = 0; i < 8; ++i) {      cout << i;    }    cout << Endl;    Loop<8>::run ();    cout << Endl;

The output is:

Test 2:template recursive for Loop unrolling0123456701234567

To achieve the above simulation for loop effect, you need to define a loop class:

Template<int N>class Loop {public:  static inline int Run () {    int v = loop<n-1>::run ();    cout << v;    return v + 1;  }}; Template<>class loop<0> {public:  static inline int Run () {    return 0;  }};

This shows how the for loop expands, because there is no recursion and looping in the compiled code. Some are a lot of special class Loop<8>, Loop<7> The run () method is executed by the loop<0>. Execute code similar to the following:

Loop<8>::run (); Loop<7>::run (); Loop<6>::run ();.. Loop<0>::run ();

C + + template meta-programming three: cyclic expansion