How do I check whether a number entered is double or integer? (1 is an integer but 1.0 is double)

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I want to check if the input is Integer or double. My problem is that when I inter 1.00 (which is double) my result is integer. How I can write app that distinguish between ( 1.00 and 1 ) ??

What I have tried:

int main()
{

double a;
cin >> a;
if ( floor(a) == ceil(a) )
	cout << "Integer";
else
	cout << "Double";

    return 0;
}

Posted 25-Mar-19 2:51am

Member 14195442

Updated 25-Mar-19 8:22am

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CPallini · Answer 1 · 2019-03-25T04:21:00

Solution 4

Check the string Luke, check the string!
(search for the dot)

You might also use std::strtol[^] providing (and the checking) the str_end parameter.

Posted 25-Mar-19 4:21am

CPallini

Updated 25-Mar-19 4:25am

v2

OriginalGriff · Answer 2 · 2019-03-25T03:03:00

Solution 1

The only way to tell is to read it as a string instead of a double, and manually parse that. Once you have read it into a double, there is no way to tell what the user actually entered.

Posted 25-Mar-19 3:03am

OriginalGriff

Comments

Member 14195442 25-Mar-19 9:43am

I am required to read as double not a string

Dave Kreskowiak 25-Mar-19 10:53am

There's no way to do that. Once you parse the string as a double, "1" and "1.00" are identical as far as the content of your a variable.

If you insist on only using a single variable of type double, the only way to tell the difference is to examine the string that was entered at the console and look for the decimal separator before you try to parse the string as a double.

#realJSOP · Answer 3 · 2019-03-25T03:04:00

Solution 2

You can use sscanf to make the value a string, and then evaluate the string. Google is your friend.

Posted 25-Mar-19 3:04am

#realJSOP

Comments

Member 14195442 25-Mar-19 9:44am

so there is no direct way to determine if it is integer or double?

#realJSOP 25-Mar-19 11:45am

Not in c++. Of course, you could write function to do it so you don't have to deal directly with the ugly bits.

Richard MacCutchan · Answer 4 · 2019-03-25T03:53:00

Solution 3

If the user enters 2 or 2.0 the resulting value is the same. There is no way to determine what was actually typed.

Posted 25-Mar-19 3:53am

Richard MacCutchan

KarstenK · Answer 5 · 2019-03-25T08:22:00

Solution 5

You must fetch the input as string and THAN convert.

You may also search that string for a "."character/substring!!! :-O

Posted 25-Mar-19 8:22am

KarstenK

Comments

Richard Deeming 26-Mar-19 15:56pm

* "THEN" convert. :)