WindChill example:

/+
 '  Wind Chill for exposed human skin, expressed as a function of wind
 '  speed in Miles per Hour and temperature in degrees Fahrenheit.
 '
 '  Public domain from numerous published references.
 '
 '  To Compile: C:\dmd\MKod_ex>dmd windchill.d
 '
 '  02.Oct.04 Compiled and Tested with dmd v0.102
 '  04.Jun.06 Compiled and Tested with dmd v0.160
 '  10.Jan.07 Compiled and Tested with dmd v1.0 
 '
 +/
 
private import std.math;
private import std.stdio;

/+
 ' Returns the Degrees that exposed human skin feels after
 ' calculating the current temperature and windspeed together.
 '
 ' -- cDegreeType --
 ' 'F' = Fahrenheit
 ' 'C' = Celsius
 '
 +/  
double windchill
(
    in double dtemperature,
    in int    iwindspeed,
    in char   cDegreeType = 'F' 
)
{
    double dWindChill = 0.0;
    
    if ( cDegreeType == 'C' || cDegreeType == 'c' )
    {
        dWindChill = convertCelsius2Fahrenheit( dtemperature );
    }
    
    if ( 4 > iwindspeed )
        dWindChill = dtemperature;
    else
    {
        dWindChill =  ( ( ( 10.45 + ( 6.686112 * sqrt( cast(double)iwindspeed ) )
                      - ( .447041 * iwindspeed ) ) / 22.034 * ( dtemperature - 91.4 ) ) + 91.4 );
    }
    
    if ( cDegreeType == 'C' || cDegreeType == 'c' )
        return convertFahrenheit2Celsius( dWindChill );
    else
        return dWindChill;    
    
} // end double windchill( in double, in int, char = 'F' )

int main()
{
    writefln( "Wind Chill for:" );
    writefln( "32.0 Fahrenheit, 15mph winds...%3.1f Fahrenheit", windchill( 32.0, 15 ) );
    writefln( "45.0 Fahrenheit, 17mph winds...%3.1f Fahrenheit", windchill( 45.0, 17 ) );
    
    writefln();
    
    writefln( "convertFahrenheit2Celsius( 32.0 ) = %3.1f Celsius", convertFahrenheit2Celsius( 32.0 ) );
    writefln( "convertFahrenheit2Celsius( 45.0 ) = %3.1f Celsius", convertFahrenheit2Celsius( 45.0 ) );
    
    writefln();
    
    writefln( "Wind Chill for:" );
    writefln( "0.0 Celsius, 15mph winds...%3.1f Celsius, %3.1f Fahrenheit", 
              windchill( 0.0, 15, 'C' ), windchill( convertCelsius2Fahrenheit( 0.0 ), 15 ) );
              
    writefln( "7.2 Celsius, 17mph winds...%3.1f Celsius, %3.1f Fahrenheit", windchill( 7.2, 17, 'C' ), 
              windchill( convertCelsius2Fahrenheit( 7.2 ), 17 ) );

    return 0;
    
} // end int main()

double convertFahrenheit2Celsius
(
    in double dFahrenheit
)
{    
    return ( dFahrenheit - 32 ) * 5 / 9;
   
} // end double convertFahrenheit2Celsius( in double )

double convertCelsius2Fahrenheit
(
    in double dCelsius
)
{    
    return dCelsius * 9 / 5 + 32;
     
} // end double convertCelsius2Fahrenheit( in double )  

C:\dmd\MKoD_ex>..\bin\dmd windchill.d
C:\dmd\bin\..\..\dm\bin\link.exe windchill,,,user32+kernel32/noi;

C:\dmd\MKoD_ex>windchill
Wind Chill for:
32.0 Fahrenheit, 15mph winds...11.5 Fahrenheit
45.0 Fahrenheit, 17mph winds...27.3 Fahrenheit

convertFahrenheit2Celsius( 32.0 ) = 0.0 Celsius
convertFahrenheit2Celsius( 45.0 ) = 7.2 Celsius

Wind Chill for:
0.0 Celsius, 15mph winds...-35.3 Celsius, 11.5 Fahrenheit
7.2 Celsius, 17mph winds...-31.6 Celsius, 27.3 Fahrenheit

C:\dmd\MKoD_ex>