Re: Passing pointer as member of struct to function

[Mihai Dontu <mdontu@bitdefender.com>]

-------- Original Message --------
Subject: Re: Passing pointer as member of struct to function
Date: Tue, 10 Jan 2006 16:29:50 +0200
From: Mihai Dontu <mdontu@bitdefender.com>
To: Reuben D. Budiardja <techlist@pathfinder.phys.utk.edu>
References: <200601100905.08338.techlist@pathfinder.phys.utk.edu>

Reuben D. Budiardja wrote:
> Hello,
> I have the following problem, which probably best explained if I give the 
> sample code first:
> 
> testNuclei.c:
> ---------------------
> #include <stdlib.h>
> #include <string.h>
> #include <stdio.h>
> 
> typedef struct nucleiType
>     {
>     char nucleiName[5];
>     int protonNumber; 
>     int neutronNumber;
>     } nucleiType;
> 
> typedef struct reaclibType
>     {
>     int reactionType;           
>     nucleiType * leftNuclei[2]; 
>     nucleiType * rightNuclei[2];
>     double QValue;
>     } reaclibType;
> 
> int setNuclei(nucleiType * nuclei);
> char * getNucleiName(nucleiType * nuclei);
> 
> int main(int argc, char ** argv)
>   {
>   reaclibType reactionRates[100];
>   nucleiType * myNuclei;
>   
>   /* Let's set the leftNuclei using the setNuclei function.  
>      We want leftNuclei to point to a valid nuclei (which is 
>      set in the function) */   
>   setNuclei(reactionRates[1].leftNuclei[0]);
     setNuclei(&(reactionRates[1].leftNuclei[0]));
>   
>     /* Now let's see if the leftNuclei has been set */
>   myNuclei = reactionRates[1].leftNuclei[0];
>   printf("reactionRate leftNuclei: %s\n", myNuclei->nucleiName);
> 
>   return 0;
>   }
> 
> /* Function to set the nuclei in the reaclibType */
> 
> int setNuclei(nucleiType * nuclei)
   int setNuclei(nucleiType ** nuclei)
>   {
>   nucleiType * newNuclei;
>   
>    /* Create new nuclei 
>     (in the real program this is defined elsewhere 
>      and read from data file 
>   */ 
>   newNuclei = (nucleiType *) malloc(sizeof(nucleiType));
>   strcpy(newNuclei->nucleiName, "sc32");
>   newNuclei->protonNumber = 21; 
>   newNuclei->neutronNumber = 11;
>   
>   // Now trying to set the passed nuclei to this newNuclei 
>   nuclei = newNuclei;
     *nuclei = newNuclei;
>   
>   return 0;
>   }
> ------------------------------------------------------------------------------------
> 
> As you can probably guess already, my problem is that I want to be able to set 
> the leftNuclei[i], which is a member of a struct reaclibType in the main 
> program through a function. When I run this program, the output that I get 
> is:
> $ ./a.out 
> reactionRate leftNuclei: (null)
> 
> What I really want is to get the following output:
> 
> $ ./a.out 
> reactionRate leftNuclei: sc32
> 
> Any help on this ? Am I confusing something ? Help would be greatly 
> appreciated. Thanks in advance.
> RDB




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