Why This doesn't work and the other one works?

Ok matsp.. the problem is that it's not compiling!

i get a compile time error. Leaving apart the logical errors like not allocating memory just i want to the syntactical error! in the definition of the 2 functions! why 1 ones and other one even though it's exactly same not working??

i get a compile time error "Undefined Structure student"

Quote:

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These both function declarations mean the same thing. Don't they?then when i call sort(student []); i get a error like undefined structure student
WHy SO???

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What do you mean by calling that function like that???

You have declared the same friend function twice, using different notation, but compilers would accept either (you shouldn't use both, though). Care to post updated code, because your code had very many problems related to memory management, any of which would be enough to make the code "not work".

Ok fine this is the new updated code

Code:

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#include <iostream.h>
#include <string.h>
class student
{
  char *name,roll[3];
  public:
        student()
        {

        }
        student(char *n,char *r)
        {
                name=new char[20];
                strcpy(name,n);
                strcpy(roll,r);
        }
  friend void sort(student []); //Why This Doesn't Work? A compile time error like "undefined structure student"

};
void sort(student a[])        //Why Not Working??
{
  int j;
  student temp;
  for(int i=0;i<3;i++)
  {
        for(j=0;j<2;j++)
        {
                if (strcmp(a[j].roll,a[j+1].roll)>0)
                {
                        temp=a[j];
                        a[j]=a[j+1];
                        a[j+1]=temp;
                }
        }
  }
}


int main(void)
{
 student a[3];
 a[0]=student("abc","1");
 a[1]=student("def","2");
 a[2]=student("hij","3");

 sort(a);

 return 0;
}

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The code you have just posted works just fine in g++ - perhaps it's ye olde compiler you are using? - it even runs without crashing - although it produces no output (aside from the "Done" that I added to see that it finishes).

--
Mats

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//Why This Doesn't Work? A compile time error like "undefined structure student"

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What compiler are you using? It looks correct and compiles on MSVC8, at least after I changed the pre-standard <iostream.h> to <iostream> (but it is not needed anyway). You should also change <string.h> to <cstring>, and indent your code more consistently.

OR you can get Visual Studio Express and let it automatically indent for you.

Quote:

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OR you can get Visual Studio Express and let it automatically indent for you.

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Note that other IDEs and specialised tools can also "beautify" code, but ultimately it is good practice to get into the habit of consistent formatting as you type your code.