RE: [Dev-C++] Passig by Reference Question

[Ioannis V. <iv...@em...>]

> -----Original Message-----
> From: dev...@li...
> [mailto:dev...@li...] On Behalf
> Of Andrι Macαrio Barros
> Sent: Thursday, April 03, 2003 8:25 PM
> To: Dev-Cpp-Users
> Subject: [Dev-C++] Passig by Reference Question
>
>
> Dear Sirs (and Ladies, if you are here),
>
>    Please, consider the three simple codes as follows:
>
> ##############################
> Program 1:
> 1 -#include <stdio.h>
> 2 -#include <stdlib.h>
> 3 -
> 4 -int sum(int, int);
> 5 -
> 6 -int main()
> 7 -{
> 8 -   int a, b, c;
> 9 -
> 10-   printf("Two Numbers Sum\n");
> 11-   printf("Enter First Number-->");
> 12-   scanf("%d", &a);
> 13-   printf("Enter Second Number-->");
> 14-   scanf("%d", &b);
> 15-   c = sum(a,b);
> 16-   printf("Sum of %d with %d is %d\n", a, b, c);
> 17-   system("PAUSE");
> 18-   return 0;
> 19-}
> 20-
> 21-int sum(int op1, int op2)
> 22-{
> 23-   int res;
> 24-
> 25-   res = op1 + op2;
> 26-   return(res);


or  return op1+op2; directly (but in reality sum() is not needed anyway).


> 27-}
> ##############################
> Program 2:
> 1 -#include <stdio.h>
> 2 -#include <stdlib.h>
> 3 -
> 4 -void sum(int, int, int *);
> 5 -
> 6 -int main()
> 7 -{
> 8 -   int a, b, c;
> 9 -
> 10-   printf("Two Numbers Sum\n");
> 11-   printf("Enter First Number-->");
> 12-   scanf("%d", &a);
> 13-   printf("Enter Second Number-->");
> 14-   scanf("%d", &b);
> 15-   sum(a, b, &c);
> 16-   printf("The Sum of %d with %d is %d\n", a, b, c);
> 17-   system("PAUSE");
> 18-   return 0;
> 19-}
> 20-
> 21-void sum(int op1, int op2, int *res)
> 22-{
> 23-   *res = op1 + op2;
> 24-
> 25-   return;


return statement is not needed here.



> 26-}
> ##############################
> Program 3:
> 1 -#include <stdio.h>
> 2 -#include <stdlib.h>
> 3 -
> 4 -void sum(int, int, int *);
> 5 -
> 6 -int main()
> 7 -{
> 8 -   int a, b, *c;
> 9 -
> 10-   c=(int *) malloc(sizeof(int));


Casting after malloc(), calloc() and realloc() IS NOT needed in C. K&R2 uses
casting because they tried the code in that time Storustrup's C++ compiler.
K&R2 also doesn't place a return statement before the end of main() which
was not proper C90. I assume that at least the first was fixed in later
editions.


So the above should be:

c=malloc(sizeof(int));

or (better):

c=malloc(sizeof(*c));





> 11-   printf("Two Numbers Sum\n");
> 12-   printf("Enter First Number-->");
> 13-   scanf("%d", &a);
> 14-   printf("Enter Second Number-->");
> 15-   scanf("%d", &b);
> 16-   sum(a, b, c);
> 17-   printf("The Sum of %d with %d is %d\n", a, b, *c);
> 18-   system("PAUSE");
> 19-   return 0;
> 20-}
> 21-
> 22-void sum(int op1, int op2, int *res)
> 23-{
> 24-   *res = op1 + op2;
> 25-   return;


return; not needed.



> 26-}
> ################
> Fight Between Programmers Scenario:
> A-I prefer to use program 2 instead of program 3 to
> demonstrate the way how
> to use passing
>   by reference over the original passing by value program 1.
> I prefer it
> because I find this
>   kind of manipulation in the books and itsn´t necessary to change the
> nature of the variables
>   (c integer variable in this case- look for line 8 in P2 and
> line 8 in P3);
> B-If we are already inside a function, and this function
> needs to pass a
> pointer variable to
>   other funcion, ok, is only use a passing way like line 16
> of Program 3
> (integer pointer c
>   variable in this case).
> ################
> My Question:
> Q1-Are both Programs, 2 and 3, correct? Please comment.
> Q2-Any opposition about my opinion in "A" Scenario?
> Q3-Any opposition about my opinion in "B" Scenario?
> Q4-Any additional comments?


See my comments above.




Ioannis Vranos

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