C++ lrint()

The lrint() function in C++ rounds the argument to an integral value using the current rounding mode.

The lrint() function in C++ rounds the argument to an integral value using the current rounding mode. The current rounding mode is determined by the function `fesetround()`. It is similar to rint(), but returns `long int`.

lrint() prototype [As of C++ 11 standard]

```long int lrint(double x);
long int lrint(float x);
long int lrint(long double x);
long int lrint(T x); // For integral type
```

The lrint() function takes a single argument and returns a value of type `long int`. This function is defined in <cmath> header file.

lrint() Parameters

The lrint() function takes a single argument value to round.

lrint() Return value

The lrint() function rounds the argument x to an integral value, using the rounding direction specified by fegetround() and returns the value in `long int`.

By default, the rounding direction is set to 'to-nearest'. The rounding direction can be set to other values using fesetround() function.

Example 1: How lrint() works in C++?

``````#include <iostream>
#include <cmath>
#include <cfenv>
using namespace std;

int main()
{
// by default, rounding direction is to-nearest i.e. fesetround(FE_TONEAREST)
double x = 11.87;
long int result;
result = lrint(x);
cout << "Rounding to-nearest (" << x << ") = " << result << endl;

// mid-way values are rounded off to higher integer
x = 11.5;
result = lrint(x);
cout << "Rounding to-nearest (" << x << ") = " << result << endl;

// setting rounding direction to DOWNWARD
fesetround(FE_DOWNWARD);
x = 11.87;
result = lrint(x);
cout << "Rounding downward (" << x << ") = " << result << endl;

// setting rounding direction to UPWARD
fesetround(FE_UPWARD);
x = 33.32;
result = lrint(x);
cout << "Rounding upward (" << x << ") = " << result << endl;

return 0;
}``````

When you run the program, the output will be:

```Rounding to-nearest (11.87) = 12
Rounding to-nearest (11.5) = 12
Rounding downward (11.8699) = 11
Rounding upward (33.3201) = 34```

Example 2: lrint() function for integral types

``````#include <iostream>
#include <cmath>
#include <cfenv>
using namespace std;

int main()
{
int x = 15;
long int result;

// setting rounding direction to DOWNWARD
fesetround(FE_DOWNWARD);
result = lrint(x);
cout << "Rounding downward (" << x << ") = " << result << endl;
return 0;
}

``````

When you run the program, the output will be:

```Rounding downward (15) = 15
```

For integral values, applying the lrint function returns the same value as the input. So it is not commonly used for integral values in practice.