Thread: Problem.

Here is the problem i have to solve.

In main, i declare a matrix, mat[12][24]
Then I call a funtion and send it the adresse of my matrix as a parameter.

In this new sub function, i am supposed to send the adresse of a row of my matrix to a second function wich then fills colomuns 7 to 19 of the row it received.

The output is simply wrong, it sould be:

0
0
0
0
0
0
6
7
8
9
10
11
12
13
14
15
16
17
0
0
0
0
0
0

times 12 because there are 12 rows.

Code:

#include <stdio.h>
#include <stdlib.h>
#include <math.h>

float fonction(float[][24]);
float rayonnementJour(float*);

int i, h, p;

int main()
{    float mat[12][24];
      
      fonction(mat);
                 
      i = 0;
      do
      {
      for(h = 0; h < 24; h++)
            {
            printf("\n &#37;f ", mat[i][h]);
            }
      printf("\n");
      i += 1;
      }while(i < 12);
      
      system("PAUSE");
      return 0;
}

float fonction(float mat[][24])
{                 
      for(i = 0; i < 12; i++)
            {
                 rayonnementJour(mat[i]);
            }
}

float rayonnementJour(float *heureptr)
{     
      *heureptr += 6;
      for(h = 6; h < 18; h++)
            {
                 *heureptr = h;
                 *heureptr++;
            }
      
}

the output for the first row is this, and the other rows all have the twelve first numbers in comon exept the 12 following are stranger:

6.000000
7.000000
8.000000
9.000000
10.000000
11.000000
12.000000
13.000000
14.000000
15.000000
16.000000
17.000000
0.000000
0.000000
0.000000
0.000000
0.000000
0.000000
0.000000
0.000000
0.000000
0.000000
6070641818228166000000000000000000000.000000
0.000000

Again ty very very much. You are my new best friend.

Do you know why *heureptr += 6; did not work?

Im guessing because *heureptr += 6; was trying to save the value 6 in the memory spot allocated to row[i][0]
But i didnt see that because my loop would right over it.

Originally Posted by Tyrant

Again ty very very much. You are my new best friend.

Do you know why *heureptr += 6; did not work?

it did'n work because:

heureptr is an address (say a 32-bit unsigned integer in 32-bit architectures)
*heureptr is the value inside that particular address of memory.

for example:

Code:

char a[3] = "ab"

a is an address, suppose it is 2345532341
you have that a points to the first char of the string (that is 'a') and you get it with *a or a[0]
(a+1)=2345532341+1=2345532342 point to the second char of the string (that is 'b')

Is it more clear?