1: //accumulate2a.cpp
3: #include <iostream>
4: #include <vector>
5: #include <numeric>
6: using namespace std;
8: /**
9: Finds the product of two integers.
10: Pre:\n a and b contain integer values.
11: Post:\n The product of a and b has been returned.
12: */
13: int product
14: (
15: int a, //in
16: int b //in
17: )
18: {
19: return a*b;
20: }
22: int main()
23: {
24: cout << "\nThis program illustrates the use of the STL accumulate() "
25: "algorithm (expanded\nversion) from <numeric> to find the "
26: "product of integers in a vector, using a\nprogrammer-defined "
27: "function to compute the product of two integers.";
28: cout << "\nPress Enter to continue ... "; cin.ignore(80, '\n');
30: vector<int> v{2, 4, 6, 8, 10}; //since C++11
31: cout << "\nHere are the integer values in the vector:\n";
32: for (int i : v) cout << i << " "; //since C++11
33: cout << "\nPress Enter to continue ... "; cin.ignore(80, '\n');
35: cout << "\nThe product of these values is "
36: << accumulate(v.begin(), v.end(), 1, product) << ".";
37: cout << "\nPress Enter to continue ... "; cin.ignore(80, '\n');
39: cout << "\nThe product of the middle three values and an intial "
40: "value of -5 is "
41: << accumulate(v.begin()+1, v.end()-1, -5, product) << ". ";
42: cout << "\nPress Enter to continue ... "; cin.ignore(80, '\n');
44: cout << "\nThe product of the values in an empty range, with "
45: "an intial value of 22, is "
46: << accumulate(v.begin(), v.begin(), 22, product) << ".";
47: cout << "\nPress Enter to continue ... "; cin.ignore(80, '\n');
48: }