Re: [Dev-C++] Question about increment..

[Reid T. <Rei...@at...>]

On Thu, 2012-09-20 at 12:54 -0400, Mani wrote:
> Hi,
> 
> I recently to try some toy things in DevC++ (version I am using is 4.9.9.2)
> 
> The code I had was this:
> 
>     int a = 1, b = 2;
>     int c = a++ + b++ + a + b;
> 
>     cout << "a = " << a << endl;
>     cout << "b = " << b << endl;
>     cout << "c = " << c << endl;
> 
> I expected the c value to be 8 (by operator precedence, ++ has higher
> precedence than +, so do in order:
> a++, then b++
> then do (a++ + b++)
> then add the previous result and a
> then add the previous result and b
> 
> but the answer I got was 6..
> 
> what might be the reason for this..??
> 
> thanks, murali
> 
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[16:06:54][94s] rthompso@raker2> ~ 
$ cat helloworld.c 
#include <stdio.h>
#include <stdlib.h>
int main(void)
{
    int a = 1, b = 2;
    int c = a++ + b++ + a + b;

    printf("c is %d\n", c);
    a = 1;
    b = 2;
    c = ++a + ++b + a + b;

    printf("c is %d\n", c);

    return 0;

}

[16:07:01][0s] rthompso@raker2> ~ 
$ cat Hello.cs 
using System;
 
class Program
{
    static void Main()
    {
        int a = 1, b = 2;
        int c = a++ + b++ + a + b;

        Console.WriteLine(c);
        Console.WriteLine("Hello world!");

        a = 1;
        b = 2;
        c = ++a + ++b + a + b;
        Console.WriteLine(c);
        Console.WriteLine("Hello world!");


        a = 1;
        b = 2;
        c = a++ + b++;
        int d =  c + a + b;

        Console.WriteLine(d);
    }
}

[16:07:26][0s] rthompso@raker2> ~ 
$ ./a.out
c is 6
c is 10

[16:07:30][0s] rthompso@raker2> ~ 
$ mono Hello.exe
8
Hello world!
10
Hello world!
8


gcc C
n++ -> increment after use
>     int a = 1, b = 2;
>     int c = a++ + b++ + a + b;
          c = 1 + 2 + 1 + 2
          c = 6

++n -> increment before use
>     int a = 1, b = 2;
>     int c = ++a + ++b + a + b;
          c = 2 + 3 + 2 + 3
          c = 10
    
mcs csharp
evidently creates an incremented copy and uses it with the original
value
>     int a = 1, b = 2;
>     int c = a++ + b++ + a + b;
          c = 2 + 3 + 1 + 2
          c = 8

++n -> increment before use
>     int a = 1, b = 2;
>     int c = ++a + ++b + a + b;
          c = 2 + 3 + 2 + 3
          c = 10

        a = 1;
        b = 2;
        c = a++ + b++;
        int d =  c + a + b;
        c = 5
        d = 5 + 1 + 2 
        d = 8