accumulate.cpp

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//: C05:Accumulate.cpp
// Passes a "function" as a parameter at compile time
#include <iostream>
using namespace std;
// Accumulates the results of F(0)..F(n)
template<int n, template<int> class F>
struct Accumulate {
   enum {val = Accumulate<n-1, F>::val + F<n>::val};
};
// The stopping criterion (returns the value F(0))
template<template<int> class F>
struct Accumulate<0, F> {
   enum {val = F<0>::val};
};
// Various "functions":
template<int n>
struct Identity {
   enum {val = n};
};
template<int n>
struct Square {
   enum {val = n*n};
};
template<int n>
struct Cube {
   enum {val = n*n*n};
};
int main() {
   cout << Accumulate<4, Identity>::val << endl; // 10
   cout << Accumulate<4, Square>::val << endl;   // 30
   cout << Accumulate<4, Cube>::val << endl;     // 100
} ///:~