What is the round() function in D?

Overview

The round() function in D rounds a number off to the nearest integer.

If the fractional part >= 0.5 then the number is rounded up.
If the fractional part < 0.5 then the number is rounded down.

The image below shows a visual representation of the round() function:

Syntax

Syntax for the round() function is given below:

round(number)
// number should be float, double or real.

Parameter

This function requires a number as a parameter.

Return value

The round() function returns the nearest integer value of a number.

Note: If -0.0, real.infinity, real.infinity, real.nan, or -real.nan is sent as a parameter then it returns the parameter as it is.

Example

The code below shows the use of the round() function in D:

import core.stdc.stdio;
import std.stdio;
//header required for function
import std.math;
int main()
{
    //integer
    writeln ("The value of round(4.0) : ",round(4.0));
    //positive double value
    writeln ("The value of round(2.56) : ",round(2.56));
    writeln ("The value of round(2.3) : ",round(2.3));
    
    //negative double value
    writeln ("The value of round(-2.56) : ",round(-2.56));
    writeln ("The value of round(-2.3) : ",round(-2.3));
    //exceptional outputs
    writeln ("The value of round(-0.0) : ",round(-0.0));
    writeln ("The value of round(real.infinity) : ",round(real.infinity));
    writeln ("The value of round(-real.infinity) : ",round(-real.infinity));
    writeln ("The value of round(real.nan) : ",round(real.nan));
    writeln ("The value of round(-real.nan) : ",round(-real.nan));
    return 0;
}

Explanation

Line 4: We add the header std.math required for the round() function.
Line 9: We round the integer value using round().
Line 12: We round the positive double value (fractional part >= 0.5) using round().

Line 13: We round the positive double value (fractional part < 0.5) using round().
Line 16: We round the negative double value (fractional part >= 0.5) using round().
Line 17: We round the negative double value (fractional part <= 0.5) using round().
Line 19: We round the exceptional numbers using round().