You can do the same thing in C#:
public static Func<double, string> makeConverter(string toUnit, double factor, double offset = 0.0)
{
return (input) => string.Format("{0:0.##} {1}", (offset + input) * factor, toUnit);
}
public static void Main()
{
var milesToKm = makeConverter("km", 1.60936);
var poundsToKg = makeConverter("kg", 0.45460);
var farenheitToCelsius = makeConverter("degrees C", 0.5556, -32);
Console.WriteLine("{0}", milesToKm(10));
Console.WriteLine("{0}", poundsToKg(2.5));
Console.WriteLine("{0}", farenheitToCelsius(98));
}
You can further reduce it down to a single method:
public static void Main()
{
Func<string, double, double, Func<double, string>> makeConverter =
(toUnit, factor, offset) => (input) => string.Format("{0:0.##} {1}", (offset + input) * factor, toUnit);
var milesToKm = makeConverter("km", 1.60936, 0.0);
var poundsToKg = makeConverter("kg", 0.45460, 0.0);
var farenheitToCelsius = makeConverter("degrees C", 0.5556, -32);
Console.WriteLine("{0}", milesToKm(10));
Console.WriteLine("{0}", poundsToKg(2.5));
Console.WriteLine("{0}", farenheitToCelsius(98));
}
You can even use old-style can use C# 2 syntax (yes, C# has had closure since 2005)
public delegate string del_t(double input);
public static del_t makeConverter(string toUnit, double factor, double offset = 0.0)
{
return delegate(double input)
{
return string.Format("{0:0.##} {1}", (offset + input) * factor, toUnit );
};
}
public static void Main()
{
var milesToKm = makeConverter("km", 1.60936);
var poundsToKg = makeConverter("kg", 0.45460);
var farenheitToCelsius = makeConverter("degrees C", 0.5556, -32);
Console.WriteLine("{0}", milesToKm(10) );
Console.WriteLine("{0}", poundsToKg(2.5) );
Console.WriteLine("{0}", farenheitToCelsius(98));
}
For comparison, if you didn't use closure, the traditional class-based way of solving this problem in C# would be:
public static void Main()
{
var milesToKm = new Converter("km", 1.60936);
var poundsToKg = new Converter("kg", 0.45460);
var farenheitToCelsius = new Converter("degrees C", 0.5556, -32);
Console.WriteLine("{0}", milesToKm.Convert(10) );
Console.WriteLine("{0}", poundsToKg.Convert(2.5) );
Console.WriteLine("{0}", farenheitToCelsius.Convert(98) );
}
class Converter
{
string m_toUnit;
double m_factor;
double m_offset;
public Converter(string toUnit, double factor, double offset = 0)
{
m_toUnit = toUnit;
m_factor = factor;
m_offset = offset;
}
public string Convert(double input)
{
return string.Format("{0:0.##} {1}", (m_offset + input) * m_factor, m_toUnit );
}
}