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I found something funny in C

 
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Singachea
fourth grade


Joined: 19 Nov 2005
Posts: 258
PostPosted: Wed May 10, 2006 9:14 pm    Post subject: I found something funny in C Reply with quote
Code:
#include<stdio.h>

void main(void)
{
   
   int i;
   for(i = 0; i = 3; i++)
   {
      printf("funny?\n");
   }

}


What is the output of this code in C language? Wink
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guitarman
fourth grade


Joined: 04 Nov 2005
Posts: 724
PostPosted: Thu May 11, 2006 1:09 pm    Post subject: Reply with quote


an Endless loop???
Wow, Never try the condition of Eqaul sign before ehh..
Innovative Smile
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Singachea
fourth grade


Joined: 19 Nov 2005
Posts: 258
PostPosted: Thu May 11, 2006 11:55 pm    Post subject: Reply with quote
Can anyone explain why?
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guitarman
fourth grade


Joined: 04 Nov 2005
Posts: 724
PostPosted: Fri May 12, 2006 12:22 am    Post subject: Reply with quote
So... my answer is right??
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Singachea
fourth grade


Joined: 19 Nov 2005
Posts: 258
PostPosted: Fri May 12, 2006 12:48 am    Post subject: Reply with quote
yes, you are right brother, but i just wonder why. Is it the flaw in C or what?
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guitarman
fourth grade


Joined: 04 Nov 2005
Posts: 724
PostPosted: Fri May 12, 2006 1:10 am    Post subject: Reply with quote
for(i = 0; i = 3; i++)

I think first i is initialized to 0, next it checks the condition i = 3 (this is always true, as i was assigned to 3), so the first print statement fires. AFterwhich, i is incremented to 1, then the condition is still true.. next... next... always true.

I think the cue point is the condition>> i = 3. Instead, it should be i==3.
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Singachea
fourth grade


Joined: 19 Nov 2005
Posts: 258
PostPosted: Fri May 12, 2006 11:07 am    Post subject: Reply with quote
I think it's not an assignment.

for(i = 0; i = 3; i++)

i = 3 is the condition

and another: for(i = 0, i = 3; ; i++)

i = 3 is an assignment where the condition is always true.

Actually we can see this:

Code:
for(initialization; condition; update)
{
     statements;
}


can be transformed into

Code:
initialization
while(condition)
{
     statements;
     update;
}


Thus if the statement is written as for(i = 0; i = 3; i++), it should be the same if we write:

Code:
i = 0
while(i = 3)
{
     statements;
     i++;
}


A mistake should be detected at while(i = 3)

We can't compile this statement for(i = 0; i = 3; i++) in java because it detects an error (incompatible type.)

If the condition is changed to i == 3, then there is nothing printed out.
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guitarman
fourth grade


Joined: 04 Nov 2005
Posts: 724
PostPosted: Fri May 12, 2006 2:50 pm    Post subject: Reply with quote
Nice explanation about transforming into while loop Smile

It happens a lot to me when I code in PHP. I think use .NET is better .
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