/*--------------------------------------------------
created by smtuttle at Tue May  4 17:54:07 PDT 2010
--------------------------------------------------*/
#include <fstream>   // includes iostream
#include <cmath>
using namespace std;


/*--------------------------------------------------
 Contract: sum_from_file : string -> double
 Purpose: expects the name of a file in the current working directory,
         expected to contain on its first line the number of values
         in that file, followed by that many double values, one per line;
         it then returns the sum of those values.

 Examples: if file april_wts.txt contains:
5
10.3
17.7
4
200.4
58.66
          then:
          sum_from_file("april_wts.txt") == 291.06
--------------------------------------------------*/

double sum_from_file(string input_file)
{
    ifstream input_stream;
    double sum_so_far = 0.0;
    double latest_value;
    int num_values;

    // find out how many values there are

    // (note: the open method needs an old-style char* string!
    //     calling the c_str method on a new-style string
    //     returns that string in char* type...)

    input_stream.open(input_file.c_str());
    input_stream >> num_values;

    // read in and sum that many values

    for (int i=0; i < num_values; i++)
    {
        input_stream >> latest_value;
        sum_so_far += latest_value;
    }

    return sum_so_far;
}