ex10_3_4.cpp

//! @Alan
//!
//! Exercise 10.3:
//! Use accumulate to sum the elements in a vector<int>.
//!
//! Exercise 10.4:
//! Assuming v is a vector<double>, what, if anything,
//! is wrong with calling accumulate(v.cbegin(), v.cend(), 0)?
//  Check the comments below.
//!

#include <iostream>
#include <string>
#include <vector>
#include <algorithm>
#include <numeric>

//! Exercise 10.3
int
accumulate_int_fromVec(const std::vector<int> &v);

int main()
{
    //! Exercise 10.3
    std::vector<int> v = {1,2,3,4};
    std::cout << accumulate_int_fromVec(v) << " ";


    //! Exercise 10.4
    std::vector<double> vd = {1.1, 0.5, 3.3};
    std::cout << std::accumulate(vd.cbegin(), vd.cend(), 0);
    //!                                                  ^
    //! The ouput is 4 rather than 4.9.
    //! The reason is std::accumulate is a template function. The third parameter is _Tp __init
    //! When "0" , an integer, had been specified here, the compiler considered _Tp should been
    //! an interger.As a result ,when the following statments were being excuted :
    //  for (; __first != __last; ++__first)
    //	__init = __init + *__first;
    //  return __init;
    //! all calculation would be converted to integer.

    return 0;
}

//! Exercise 10.3
int accumulate_int_fromVec(const std::vector<int> &v)
{
    return std::accumulate(v.cbegin(), v.cend(), 0);
}