Why is this NaN

Question

Im trying to run the following code

  int salespersons=0,weeks=0,days=5;

  double weekly_sales[weeks][salespersons][days];
  double total_weekly_sales[weeks];


for(int w=0; w < weeks;w++)
  {
     for(int d =0; d < days; d++)
     {  

        for(int s=0; s < salespersons; s++)
        {

           {
              total_weekly_sales[w]+=weekly_sales[w][s][d];
              total_overall_weekly_sales[s]+= weekly_sales[w][s][d];

           }
        }  
     }

  }

when I run only..

cout << total_weekly_sales[0];

I get NaN therefore skipping the first section of the array while processing the rest.

Can you show us where you've initialized `total_weekly_ales` and `weekly_sales`? Are you sure that none of those values are `NaN`? — templatetypedef, Apr 04 '13 at 19:18
@BarışUşaklı that statement is misleading. are we supposed to assume more? — scones, Apr 04 '13 at 19:19
@DrewDormann I suggest you write [`i = i++ + ++i;`](http://stackoverflow.com/questions/949433/could-anyone-explain-these-undefined-behaviors-i-i-i-i-i-etc) — , Apr 04 '13 at 19:23

score 5 · Accepted Answer · 2013-04-04T19:28:00.060

5

double weekly_sales[weeks][salespersons][days];
double total_weekly_sales[weeks];

Uninitialized.

Edit: this is how you should initialize them:

double weekly_sales[weeks][salespersons][days] = { { { 0.0 } } };

edited Apr 04 '13 at 19:28

answered Apr 04 '13 at 19:19

How would I initialize this properly. I further defined my question for clarity. – Apr 04 '13 at 19:24
Hopefully just `= {0.0}` will work soon enough if the proposal goes well. – chris Apr 04 '13 at 19:33
Just adding = { { { 0.0 } } }; makes it give the error "variable-sized object 'weekly_sales' may not be initialized" – Apr 04 '13 at 19:38
I found that adding weekly_sales[0][0][0]=0; total_weekly_sales[0]=0; makes it work – Apr 04 '13 at 19:46
@Some guy: That is because the dimensions of the array are not constant. Change the line `int salespersons=0,weeks=0,days=5;` to `int const salespersons=0,weeks=0,days=5;` – Arun Apr 04 '13 at 19:47

score 2 · Answer 2 · answered Apr 04 '13 at 19:21

2

double total_weekly_sales[weeks];

total_weekly_sales[w]+=weekly_sales[w][s][d];

You are adding to an uninitialized variable.

And printing an uninitialized variable

cout << total_weekly_sales[0];

answered Apr 04 '13 at 19:21

Matt

74
3

score 1 · Answer 3 · answered Apr 04 '13 at 19:22

You try with the code and you've initialized all variables

    int weeks=2,salepersons=3,days=1;

        double weekly_sales[weeks][salespersons][days];
          double total_weekly_sales[weeks];

    for(int w=0; w < weeks;w++)
      {
         for(int d =0; d < days; d++)
         {  
        for(int s=0; s < salespersons; s++)
        {

           {
              total_weekly_sales[w]=2;
              weekly_sales[w][s][d]=1;

           }
        }  
     }

  }


    for(int w=0; w < weeks;w++)
      {
         for(int d =0; d < days; d++)
         {  

            for(int s=0; s < salespersons; s++)
            {

               {
                  total_weekly_sales[w]+=weekly_sales[w][s][d];
                  total_overall_weekly_sales[s]+= weekly_sales[w][s][d];

               }
            }  
         }

      }

And use the library!!!

Why is this NaN

3 Answers3

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