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littleguy
 Post subject: C++ Float check if integer
PostPosted: Thu Feb 14, 2008 2:48 pm 
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Joined: Tue May 24, 2005 1:19 pm
Posts: 1236
I need a couple lines of code to check if my float variable is an integer or not. I'm working on an assignment to use newton's method to compute the nth root of x and wanted to check if the user input an integer for n or not, but I don't want to use int for n because in my experience inputting something for an int that isn't an integer results in errors and program crashes. Any other ideas are welcome.

Thanks guys!
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Adak
 Post subject:
PostPosted: Thu Feb 14, 2008 3:26 pm 
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You can input the variable as an integer, then reassign it to your float, or cast it.

Code:
int truncate, i;
float myFloat;
i = 0;
do  {
}while (i (scanf("%d", &truncate)) != 1);

myFloat = truncate;  /* implicit cast to float before assignment */


I haven't ran the above, so it may have errors, but it should give you the idea.
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littleguy
 Post subject:
PostPosted: Thu Feb 14, 2008 3:53 pm 
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Thanks!

Yeah, I kept poking around and I finally came up with a way to truncate as well as tell me if it's been truncated or not so that I can let the user know.

Code:
int number;
double numberdouble;
cout<<"Enter a number: ";
cin>>numberdouble;
number=numberdouble;
if (number!=numberdouble)
{cout<<"Number has been truncated.";}
else
......
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Kybo_Ren
 Post subject:
PostPosted: Thu Feb 14, 2008 8:54 pm 
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Joined: Fri Sep 17, 2004 5:35 pm
Posts: 1176
Yeah it's easiest to do something like
Code:
bool __inline is_integer(float f){
    int i = f;
    return (f == static_cast<float>(i));
}
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Gadget
 Post subject:
PostPosted: Mon Feb 18, 2008 6:01 pm 
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Joined: Tue Jun 29, 2004 11:32 pm
Posts: 2555
Location: Somewhere between compilation and linking
Kybo_Ren wrote:
Yeah it's easiest to do something like
Code:
bool __inline is_integer(float f){
    int i = f;
    return (f == static_cast<float>(i));
}

The correctness of you C++ code... really makes me appreciate C. =)
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