Help! Pointer difficulties.

**Tyrant** · 11-17-2007

Here is my problem, I try to compile, it says error, *heureptr undclared.... The thing is, im trying to make *heureptr point to the adress of a row in a matrix, mat[i], wich points to the matrix mat[][24].

The error occurs on line 34. witch is the line *heureptr = mat[i]

Here is my code.

Code:

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

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

float vsr[12] = {0.142, 0.207, 0.298, 0.389, 0.456, 0.483, 0.467, 0.410, 0.326, 0.234, 0.158, 0.124};
int i, h;

int main()
{     float mat[12][24];
      
      fonction(mat);

      i = 0;
      do
      {
      for(h = 0; h < 24; h++)
            {
            printf("&#37;f ", mat[i][h]);
            }
      printf("\n");
      i += 1;
      }while(i < 13);
      
      system("PAUSE");
      return 0;
}

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

float rayonnementJour(int i,float *heureptr)
{     
      float x;
      
      *heureptr + 5;
      for(h = 6; h < 19; h++)
            {
                 x = (0.2618 * (h - 12));
                 *heureptr = 2 * vsr[i] * cos(x);
                 *heureptr + 1;
            }
      
}

**matsp** · 11-17-2007

Code:

float fonction(float mat[][24])
{     int heure;
            
      for(i = 0; i < 12; i++)
            {
                 *heureptr = mat[i];
                 rayonnementJour(i, *heureptr);
            }
}

The compiler is complaining because this function does NOT have a heureptr, and it's also not a global variable.

--
Mats

**gibsosmat** · 11-17-2007

Code:

...
float fonction(float mat[][24])
{     int heure; /* I guess you wanted it to be int *heure;
            
      for(i = 0; i < 12; i++)
            {
                 *heureptr = mat[i];
                 rayonnementJour(i, *heureptr);
            }
}
...

**Tyrant** · 11-17-2007

i removed the int heure

i was hopping it would fixe the problem,

*heureptr is supposed to be a pointer i shouldnt have to declare it right?

**Tyrant** · 11-17-2007

I changed my code to this

Code:

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

float rayonnementJour(int i,float *heureptr)
{     
      float x;
      
      *heureptr + 5;
      for(h = 6; h < 19; h++)
            {
                 x = (0.2618 * (h - 12));
                 *heureptr = 2 * vsr[i] * cos(x);
                 *heureptr + 1;
            }
      
}

Now its a never ending loop but its a start.

**gibsosmat** · 11-17-2007

Originally Posted by Tyrant

i removed the int heure

i was hopping it would fixe the problem,

*heureptr is supposed to be a pointer i shouldnt have to declare it right?

yeah.. you are right..
but the definition if the variable is wrong..

what you defined is that heureptr is of type int, and NOT int pointer
if you want to use it as a pointer you should define it as int *xyz

**Tyrant** · 11-17-2007

My code is now this, theres no more a compiling error but the output is wrong.

Code:

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

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

float vsr[12] = {0.142, 0.207, 0.298, 0.389, 0.456, 0.483, 0.467, 0.410, 0.326, 0.234, 0.158, 0.124};
int i, h;

int main()
{     float mat[12][24];
      
      fonction(mat);

      i = 0;
      do
      {
      for(h = 0; h < 25; h++)
            {
            printf("&#37;f ", mat[i][h]);
            }
      printf("\n");
      i += 1;
      }while(i < 13);
      
      system("PAUSE");
      return 0;
}

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

float rayonnementJour(int i,float *heureptr)
{     
      float x;
      
      *heureptr + 5;
      for(h = 6; h < 19; h++)
            {
                 x = (0.2618 * (h - 12));
                 *heureptr = 2 * vsr[i] * cos(x);
                 *heureptr + 1;
            }
      
}

ill simplifie all the numbers.

**Salem** · 11-17-2007

> for(h = 0; h < 25; h++)
This steps off the end of the array. It should be < 24

> rayonnementJour(i, mat[i]);
Does this even compile without any warnings for you?
Or are you ignoring them?

rayonnementJour(i, &mat[i]); would at least be consistent with the prototype and definition of the function.

**Tyrant** · 11-17-2007

Originally Posted by gibsosmat

yeah.. you are right..
but the definition if the variable is wrong..

what you defined is that heureptr is of type int, and NOT int pointer
if you want to use it as a pointer you should define it as int *xyz

I did that

Code:

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

and it compiles but then gives me a windows error and i have to end task.

These warnings also appear.

36 c:\docume~1\andre\mydocu~1\lcc\mini.c
warning: assignment makes integer from pointer without a cast

37 c:\docume~1\andre\mydocu~1\lcc\mini.c
warning: passing arg 2 of `rayonnementJour' makes pointer from integer without a cast

**Tyrant** · 11-17-2007

Originally Posted by Salem

> for(h = 0; h < 25; h++)
This steps off the end of the array. It should be < 24

> rayonnementJour(i, mat[i]);
Does this even compile without any warnings for you?
Or are you ignoring them?

rayonnementJour(i, &mat[i]); would at least be consistent with the prototype and definition of the function.

your right. No, no warnings, but your right.
and i think &mat[i] and mat[i] are the same because mat[i] as to represent an adress because its a row in a matrix.

**gibsosmat** · 11-17-2007

Code:

float fonction(float mat[][24])
{     int *heureptr;// your mat[][] is type float
            
      for(i = 0; i < 12; i++)
            {    
                 *heureptr = mat[i];
                 //heureptr = mat[i]; assign address. 
                 //you are trying to put value into some pointer that is not declared
                 rayonnementJour(i, *heureptr)
            }
}

**iMalc** · 11-17-2007

*heureptr + 5;

That doesn't actually do anything.
It's like saying 1+1; to which the compiler simply goes "Whoopdeedoo!".
You need some kind of assignment or side-effect in there.

**Tyrant** · 11-17-2007

Code:

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

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

float vsr[12] = {1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12};
int i, h;

int main()
{     float mat[12][24];
      
      fonction(mat);

      i = 0;
      do
      {
      for(h = 0; h < 24; h++)
            {
            printf(" &#37;f ", mat[i][h]);
            }
      printf("\n");
      i += 1;
      }while(i < 13);
      
      system("PAUSE");
      return 0;
}

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

float rayonnementJour(int i,float *heureptr)
{     
      *heureptr + 5;
      for(h = 6; h < 19; h++)
            {
                 *heureptr = 2 * vsr[i];
                 *heureptr + 1;
            }
      
}

The output:

2.000000 1.#QNAN0 7867456191839611200000000000000000.000000 0.000000 0.0000
00 0.000000 0.000000 0.000000 0.000000 537752089363777560000000000000000000
0.000000 0.000000 6020158900724676900000000000000000000.000000 60558914358439
10300000000000000000000.000000 -1.#QNAN0 6056156374819358000000000000000000000
.000000 6068373991304357700000000000000000000.000000 0.000000 1.#QNAN0 1.#QN
AN0 6068420894376566100000000000000000000.000000 0.000000 0.000000 0.000000
0.000000
4.000000 0.000000 0.000000 0.000000 0.000000 0.000000 0.000000 0.000000
0.000000 0.000000 0.000000 0.000000 0.000000 0.000000 0.000000 0.000000
0.000000 0.000000 0.000000 0.000000 0.000000 0.000000 6070641818228166000
000000000000000000.000000 0.000000
6.000000 0.000000 0.000000 0.000000 0.000000 0.000000 0.000000 0.000000
0.000000 6070613929914960900000000000000000000.000000 0.000000 6070400964614
122600000000000000000000.000000 0.000000 1.#QNAN0 0.000000 60704187117225258
00000000000000000000.000000 0.000000 0.000000 0.000000 0.000000 0.000000 6
308463212035783600000000000000000000.000000 0.000000 0.000000
8.000000 0.000000 0.000000 0.000000 0.000000 0.000000 0.000000 537731490
0415238500000000000000000000.000000 0.000000 0.000000 0.000000 0.000000 0.0
00000 0.000000 0.000000 6024231862103210200000000000000000000.000000 0.00000
0 0.000000 6024231862103210200000000000000000000.000000 0.000000 0.000000 0
.000000 0.000000 0.000000
10.000000 0.000000 6020158900724676900000000000000000000.000000 602423566505
5010900000000000000000000.000000 -1.#QNAN0 0.000000 6026566874508830600000000
000000000000.000000 6024186860506902100000000000000000000.000000 0.000000 0.0
00000 0.000000 0.000000 0.000000 0.000000 0.000000 0.000000 6020158900724
676900000000000000000000.000000 6024235665055010900000000000000000000.000000 -
1.#QNAN0 6024231862103210200000000000000000000.000000 602414629568769480000000
0000000000000.000000 6024186860506902100000000000000000000.000000 0.000000 80
37033551211060100000000000000000.000000
12.000000 0.000000 0.000000 6018216226179827200000000000000000000.000000 53
47049742334789500000000000000000000.000000 -1.#QNAN0 7889934088102935500000000
000000000.000000 0.000000 0.000000 0.000000 0.000000 0.000000 534707572917
2094200000000000000000000.000000 -1.#QNAN0 7889934088102935500000000000000000.
000000 0.000000 0.000000 0.000000 5573104803271088800000000000000000000.0000
00 0.000000 0.000000 5658224371949913800000000000000000000.000000 7889934088
102935500000000000000000.000000 0.000000
14.000000 0.000000 0.000000 0.000000 0.000000 0.000000 0.000000 54947620
94701083800000000000000000000.000000 7889934088102935500000000000000000.000000
0.000000 0.000000 0.000000 0.000000 920466.125000 0.000000 0.000000 0.00
0000 0.000000 0.000000 0.000000 0.000000 0.000000 0.000000 0.000000
16.000000 0.000000 0.000000 0.000000 0.000000 0.000000 0.000000 0.000000
0.000000 0.000000 0.000000 0.000000 0.000000 0.000000 0.000000 0.000000
0.000000 0.000000 0.000000 0.000000 0.000000 0.000000 0.000000 0.000000

18.000000 0.000000 0.000000 6023926992133855400000000000000000000.000000 0.
000000 6023944739242258600000000000000000000.000000 0.000000 0.000000 0.0000
00 1.#QNAN0 0.000000 0.000000 -0.000000 0.000000 0.000000 0.000000 0.000
000 -0.000000 0.000000 0.000000 0.000000 -0.000000 0.000000 0.000000
20.000000 0.000000 0.000000 0.000000 0.000000 0.000000 0.000000 0.000000
0.000000 0.000000 0.000000 0.000000 0.000000 0.000000 0.000000 0.000000
0.000000 0.000000 0.000000 6024190029633402700000000000000000000.000000 0.
000000 0.000000 0.000000 0.000000
22.000000 0.000000 6020158900724676900000000000000000000.000000 602394664071
8158900000000000000000000.000000 -1.#QNAN0 60239447392422586000000000000000000
00.000000 7900452864616743400000000000000000.000000 0.000000 0.000000 790045
5959466841600000000000000000.000000 0.000000 0.000000 0.000000 7924809334889
683200000000000000000.000000 7834164889333129100000000000000000.000000 -1.#QNA
N0 7900601417421457600000000000000000.000000 0.000000 0.000000 0.000000 792
4809334889683200000000000000000.000000 7834150034052657700000000000000000.00000
0 -1.#QNAN0 7900455959466841600000000000000000.000000
24.000000 0.000000 0.000000 0.000000 7937818227792513600000000000000000.000
000 0.000000 1.#QNAN0 1.#QNAN0 0.000000 0.000000 0.000000 786688426354146
1400000000000000000.000000 0.000000 0.000000 0.000000 0.000000 0.000000 -1
.#QNAN0 0.000000 0.000000 7988459878919600000000000000000000.000000 0.000000
0.000000 0.000000
0.000000 0.000000 0.000000 0.000000 0.000000 0.000000 0.000000 0.000000
0.000000 0.000000 1.#QNAN0 -222775059167508960000.000000 0.000000 0.000000
0.000000 0.000000 0.000000 0.000000 0.000000 -0.000000 60188950530762494
00000000000000000000.000000 5376595508699609000000000000000000000.000000 -1.#Q
NAN0 0.000000
Press any key to continue . . .

somthing went terribly wrong.....

Code:

float rayonnementJour(int i,float *heureptr)
{     
      *heureptr += 5;
      for(h = 6; h < 19; h++)
            {
                 *heureptr = 2 * vsr[i];
                 *heureptr++;
            }
      
}

is my pointer arrithmetic right? Im trying to modifie colum 6 to 18 for every row...

should i start a new thread?

**Tyrant** · 11-17-2007

Originally Posted by iMalc

That doesn't actually do anything.
It's like saying 1+1; to which the compiler simply goes "Whoopdeedoo!".
You need some kind of assignment or side-effect in there.

If *heureptr dose what I want it to do:

it represents the adresse of the first row of my matrix,
when i go *heurptr + 5, im trying to tell *heureptr to become the adress of the 6th colum of the first row.

then in my loop i go plus 1 so that the column goes from 6 to 18.

**gibsosmat** · 11-17-2007

Originally Posted by Tyrant

If *heureptr dose what I want it to do:

it represents the adresse of the first row of my matrix,
when i go *heurptr + 5, im trying to tell *heureptr to become the adress of the 6th colum of the first row.

then in my loop i go plus 1 so that the column goes from 6 to 18.

either you forgot programming in C. or you dont know how to do it..
there are lot of problems in your code..

avoid inliners..
what you want to do was *heruptr+=5;..
you better put it *heruptr = *heruptr + 5;

*heruptr++; // not *heruptr + 1
is *heruptr = *heruptr + 1;

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