This question already has answers here:
Floating point format for std::ostream
(8 answers)
Closed 8 years ago.
my problem is when I am trying to print a floating-point GPA in C++.
It seems like a simple issue, but I can't get it to work. Basically I have a floating point value set to 4.0 for a GPA. However, when I try to print it like this:
cout << gpa << endl;
I get the value of 4. Without the .0 on the end. However, I want the .0 to show up. I have tried setting a precision but with no luck. Any help is appreciated.
You can use std::fixed in conjunction with std::setprecision
#include <iostream> // std::fixed
#include <iomanip> // std::setprecision
int main() {
double gpa = 4.0;
std::cout << std::fixed << std::setprecision(1) << gpa << std::endl;
return 0;
}
// Output is 4.0
#include <iomanip>
...
cout.setf(ios::fixed); // use fixed-point notation
cout.setf(ios::showpoint); // show decimal point
cout.precision(1);
...
cout << gpa << endl;
Related
This question already has answers here:
How to specify setprecision rounding
(4 answers)
Closed 1 year ago.
I'm doing my ICT homework and I ran into this problem: the decimals keep on getting rounded off when I print them. I've already included the <iomanip> header and used the fixed and setprecision manipulators, but it still keeps getting rounded off. Here's my code:
#include <iostream>
#include <iomanip>
using namespace std;
int main ()
{
double num1 = 3.12345678
cout << fixed << setprecision (4);
cout << num1 << endl;
return 0;
}
When I run the program, "3.1235" comes out instead of "3.1234," which is the expected output according to my teacher. How do I prevent the fourth decimal from rounding off?
Expanding answer of #eerorika. You can use std::fesetround() to set rounding strategy, as in code below. It outputs 3.1234 as you wished. Possible values for this function's argument are FE_DOWNWARD, FE_TONEAREST, FE_TOWARDZERO, FE_UPWARD.
Try it online!
#include <iostream>
#include <iomanip>
#include <cfenv>
int main() {
double num = 3.12345678;
std::fesetround(FE_TOWARDZERO);
std::cout << std::fixed << std::setprecision(4) << num << std::endl;
}
Output:
3.1234
3.1234 is not the expected output, setprecision will round to the specified precision.
One solution to get 3.1234 is to round to the desired number of decimal places yourself (std::trunc just rounds towards zero):
#include <cmath>
...
std::cout << std::fixed << std::setprecision(4);
std::cout << std::trunc(num1 * 10000) / 10000 << endl;
If you want to prevent rounding i.e. you want to see more precision, you can use a higher value with setprecision.
If you want to round towards zero instead of rounding towards nearest, you can use the FE_TOWARDZERO rounding mode.
This question already has answers here:
Printing the correct number of decimal points with cout
(13 answers)
Closed 1 year ago.
As a newbie in the world of programming, I have to write a bit of C++ code to find the average of two numbers.
However, my code somehow appears to be incorrect. Please take a look at my code:
#include <iostream>
using namespace std;
int main() {
float a, b, average;
cin >> a;
cin >> b;
average = (a+b)/2;
cout << average << endl;
}
however, it says I am wrong because when I input 10 10 it outputs 10 but the system wants me to output 10.00
You need to use some I/O manipulators.
std::setprecision and std::fixed
Example:
#include <iomanip>
#include <iostream>
int main() {
if(float a, b; std::cin >> a >> b) {
float average = (a+b)/2;
std::cout << std::fixed << std::setprecision(2) << average << '\n';
}
}
Like others have said you need to change your cout line to:
cout << fixed << setprecision(2) << average << endl;
Remember that with the <<s you're putting a stream of data (an iostream) into cout. The first piece of data is std::fixed which says "Display floats to a fixed number of decimal places, don't cut off any trailing zeros." And then std::setprecision(2) says "Make that fixed number of decimal places 2." You could use an int variable or another number in place of 2 if you wanted. From there the stream has your average and an endline like before.
Set decimal precision
Sets the decimal precision to be used to format floating-point values on output operations.
#include <iostream>
using namespace std;
#include <iomanip> // std::setprecision
int main() {
float a, b, average;
cin >> a;
cin >> b;
average = (a+b)/2;
cout << fixed << setprecision(2) << average << endl;
}
This question already has answers here:
Set the digits after decimal point
(7 answers)
Closed 9 years ago.
C++
I would like to cout float f = 2.3333, but only with two decimals. How do I do that?
I remember something like this, but it doesn't work:
cout << f:2 << endl;
Using stream manipulators fixed and setprecision:
#include <iomanip>
float f = 2.3333;
std::cout << std::setprecision(2) << std::fixed << f;
I managed to solve it without iomanip:
cout << (((int)f*100) % 100)/100;
This question already has answers here:
Closed 10 years ago.
Possible Duplicate:
floating point precision
when I do cout<<8.0 .Its getting printed as 8.How to Print in the output console of c++ the entire zeros after decimal point like 8.00000000
I tried this cout<<setprecision(5)<<(double)8.0; still printing 8
Use the fixed manipulator
#include <iostream>
#include <iomanip>
using namespace std;
int main() {
cout << fixed << setprecision(6) << (double)8 << "\n";
return 0;
}
http://ideone.com/ShcNIc
See How do I print a double value with full precision using cout?
cout.precision(15);
cout << fixed << 8.0;
This question already has answers here:
How do I print a double value with full precision using cout?
(17 answers)
Closed 6 years ago.
I want to output the value of a double in it's full precision. However, when using the cout function, it only displays the first 6 digits even though there is around 15-16 digits of precision.
How do I get my program to display the entire value, including the magnitude (power) component?
Use the setprecision() manipulator:
http://www.cplusplus.com/reference/iostream/manipulators/setprecision/
You can also force scientific notation with the scientific manipulator:
http://www.cplusplus.com/reference/iostream/manipulators/scientific/
cout << scientific << setprecision(15) << my_number << endl;
you could use something like this :
#include <iomanip>
cout << setprecision (9) << double_value << endl;
more iomanipulators, here
You're looking for setprecision (code taken from link):
int main () {
double f =3.14159;
cout << setprecision(15) << f << endl;
return 0;
}