[Dev-C++] RES: Dev-cpp-users digest, Vol 1 #1386 - 7 msgs

[<and...@su...>]

I spoke too much. And the main answer I was looking for was given.
-->Program 2 and Program 3 are correct programs to be used as examples of
passing by reference?
-->I say this, because I prefer Program 2 that doesn´t change the nature
of variables, ok?
-->I repost the codes, ok?

note-1: of course, is not needed the function sum in any of theese programs,
and the c variable, and the res variable! It´s a matter of explanation for
the students. I prefer to use a very simple program to explain some
operation,
beginning from a program that they already know how to write, like sum, to
present a concept not so easy to understand like passing by reference.
note-2: the cast, I explain too: some of them use the oldies Turbo C
and Turbo C++, and to avoid there the compilation error I´d agree to put the
cast.
note-3: the return? I remember that probably in HP-UX, I´m not sure, when I
used
a command-line cc program (without additional command line options) some of
the
compilation results indicated warnings in void functions that didn´t put
a final "return" command.

Regards
Andre

>--__--__--
>
>Message: 1
>From: "Ioannis Vranos" <iv...@em...>
>To: "'Dev-Cpp-Users'" <dev...@li...>
>Subject: RE: [Dev-C++] Passig by Reference Question
>Date: Thu, 3 Apr 2003 21:14:39 +0300
>
>> -----Original Message-----
>> From: dev...@li...
>> [mailto:dev...@li...] On Behalf
>> Of Andr$B&I(B Mac$B&A(Brio 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$B!-(Bt 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
>
>* Programming pages: http://www.noicys.freeurl.com
>* Alternative URL: http://run.to/noicys
>
>
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