dev-cpp-users Mailing List for Dev-C++

Hello,

It's undefined in the standard.... the sub expressions can be
calculated in any order.... ie...

= a++ + b++ + a + b;
a++ could be calculated before or after any of the following
b++ ,
a ,
b,

Since the side effects of the a++ and b++ change the value of the
later it is undefined in C or C++

See also: http://en.wikipedia.org/wiki/Unspecified_behavior

On Thu, Sep 20, 2012 at 9:50 PM, Reid Thompson <rei...@at...> wrote:
> On 9/20/2012 9:08 PM, Mani wrote:
>> I think I might argue with one point way below.. please scroll down..
>>
>> On Thu, Sep 20, 2012 at 4:08 PM, Reid Thompson <Rei...@at...> wrote:
>>> 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
>>>>
>>>> ------------------------------------------------------------------------------
>>>> Everyone hates slow websites. So do we.
>>>> Make your web apps faster with AppDynamics
>>>> Download AppDynamics Lite for free today:
>>>> http://ad.doubleclick.net/clk;258768047;13503038;j?
>>>> http://info.appdynamics.com/FreeJavaPerformanceDownload.html
>>>> _______________________________________________
>>>> Dev-cpp-users mailing list
>>>> Dev...@li...
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>>>> https://lists.sourceforge.net/lists/listinfo/dev-cpp-users
>>> [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
>>>>>> BEGIN: Murali:
>> How can you be sure that this is what happens.. I am inclined to
>> believe what happens is:
>> c = 1 + 2 + 2 + 3
>> c = 8
>>
>>>>>> END: Murali
>>> ++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
>>>
>>>
> ok -- you are most likely correct.
>
> ------------------------------------------------------------------------------
> Got visibility?
> Most devs has no idea what their production app looks like.
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> _______________________________________________
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On 9/20/2012 9:08 PM, Mani wrote:
> I think I might argue with one point way below.. please scroll down..
>
> On Thu, Sep 20, 2012 at 4:08 PM, Reid Thompson <Rei...@at...> wrote:
>> 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
>>>
>>> ------------------------------------------------------------------------------
>>> Everyone hates slow websites. So do we.
>>> Make your web apps faster with AppDynamics
>>> Download AppDynamics Lite for free today:
>>> http://ad.doubleclick.net/clk;258768047;13503038;j?
>>> http://info.appdynamics.com/FreeJavaPerformanceDownload.html
>>> _______________________________________________
>>> Dev-cpp-users mailing list
>>> Dev...@li...
>>> TO UNSUBSCRIBE: http://www23.brinkster.com/noicys/devcpp/ub.htm
>>> https://lists.sourceforge.net/lists/listinfo/dev-cpp-users
>> [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
>>>>> BEGIN: Murali:
> How can you be sure that this is what happens.. I am inclined to
> believe what happens is:
> c = 1 + 2 + 2 + 3
> c = 8
>
>>>>> END: Murali
>> ++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
>>
>>
ok -- you are most likely correct.

I think I might argue with one point way below.. please scroll down..

On Thu, Sep 20, 2012 at 4:08 PM, Reid Thompson <Rei...@at...> wrote:
> 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
>>
>> ------------------------------------------------------------------------------
>> Everyone hates slow websites. So do we.
>> Make your web apps faster with AppDynamics
>> Download AppDynamics Lite for free today:
>> http://ad.doubleclick.net/clk;258768047;13503038;j?
>> http://info.appdynamics.com/FreeJavaPerformanceDownload.html
>> _______________________________________________
>> Dev-cpp-users mailing list
>> Dev...@li...
>> TO UNSUBSCRIBE: http://www23.brinkster.com/noicys/devcpp/ub.htm
>> https://lists.sourceforge.net/lists/listinfo/dev-cpp-users
>
> [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

>>>> BEGIN: Murali:

How can you be sure that this is what happens.. I am inclined to
believe what happens is:
c = 1 + 2 + 2 + 3
c = 8

>>>> END: Murali

>
> ++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
>
>