C Programming - Floating Point Issues - Discussion

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- Alexander Pope

We want to round off x, a float, to an int value, The correct way to do is

[A].	y = (int)(x + 0.5)	[B].	y = int(x + 0.5)
[C].	y = (int)x + 0.5	[D].	y = (int)((int)x + 0.5)

Answer: Option B

Explanation:

Rounding off a value means replacing it by a nearest value that is approximately equal or smaller or greater to the given number.

y = (int)(x + 0.5); here x is any float value. To roundoff, we have to typecast the value of x by using (int)

Example:


#include <stdio.h>

int main ()
{
  float x = 3.6;
  int y = (int)(x + 0.5);
  printf ("Result = %d\n", y );
  return 0;
}

Output:
Result = 4.

Sravan said: (Mon, Aug 9, 2010 08:48:17 AM)

Is any difference between int and (int) ?

Vishak said: (Wed, Jan 26, 2011 04:43:39 AM)

@Ashish: i too thought the same why cant we ? is there a proper explanation ?

Well Wisher said: (Thu, Feb 10, 2011 12:55:39 AM)

Why we should add 0.5 to x :(x+.5) We can get the answer directly. y=(int)(x); I hope this is enough. In case the round off vale shold not be a min one then we can go for (x+0.5) Because if u type the above code having x=3.99 Then the roound off value would be 3. That is not we are looking for.

Vinoth said: (Thu, Mar 17, 2011 12:00:36 PM)

Sravan int is different from (int).in given program is compiled in C++ compiler. In C language we use paranthesis to a variable. eg:y=int (x) here x is an float variable and y is an integer variable. In C++ we put paranthesis to data type. Eg:y=(int) x eg we take x=5.6 in question asked is rounding int value(y) for given float value(x) so we add 0.5 to that number.Then the final result is 1.in C language y=int (x+0.5) 2.in C++ y=(int) (x+0.5) the result is same in both C and C++ compilers y=6. ALL THE BEST...

Anuj Kumar said: (Thu, Apr 7, 2011 04:39:21 PM)

Why we should add 0.5 to x :(x+.5) We can get the answer directly. y=(int)(x); I hope this is enough. In case the round off vale shold not be a min one then we can go for (x+0.5) Because if u type the above code having x=3.99 Then the roound off value would be 3.

Abha said: (Sat, Aug 27, 2011 09:21:17 PM)

According to me ans should be C because type castng is done to variable and not to a constant term. Tell me whether my perception is wrong or right. ?

Rani said: (Fri, Sep 9, 2011 06:45:12 PM)

But option (A)=4 option(B)=3 means both are correct we need only round off not say Floor or ceil

Kanta Patidar said: (Fri, Sep 9, 2011 06:50:12 PM)

option (a)=4 option(c)=3 option(d)=3 it means tino option is right

Vamshi Krishna said: (Fri, Nov 25, 2011 06:52:28 AM)

I think here is the question to round of x and not the y to which it is assigning so i think (int)x+0.5 is appropriate...!!! If not can anyone give me a proper explanation???

Ganga said: (Thu, Dec 29, 2011 06:34:33 PM)

What is return function can you explain for me? Why it z return0 we can also put only return know!

Bhupesh said: (Fri, Jan 20, 2012 12:19:16 AM)

if x=3.1 then y=(int)(3.1+0.5) so out put would 4 again, the float 3.1 value should be converted to int 3 only. Please let me understand this concept.