public static RecurrenceFunction composition(RecurrenceFunction f, RecurrenceFunction g)
{
return(x =>
{
if (f == null || g == null)
{
return -1;
}
var param = new int[f.GetInvocationList().Length];
for (int i = 0; i < param.Length; ++i)
{
try
{
param[i] = (int)f.GetInvocationList()[i].DynamicInvoke(x);
if (param[i] == -1)
{
return -1;
}
}
catch (Exception)
{
return -1;
}
}
try
{
return g(param);
}
catch (Exception)
{
return -1;
}
});
}
public static RecurrenceFunction primitiveRecurrence(RecurrenceFunction g, RecurrenceFunction h)
{
RecurrenceFunction result = null;
result = input =>
{
try
{
if (g == null || h == null || input[0] < 0)
{
return(-1);
}
if (input[0] == 0)
{
var x = new int[input.Length - 1];
Array.Copy(input, 1, x, 0, input.Length - 1);
return(g(x));
}
var forH = new int[input.Length + 1];
Array.Copy(input, 1, forH, 0, input.Length - 1);
--input[0];
forH[forH.Length - 2] = input[0];
forH[forH.Length - 1] = result(input);
return(h(forH));
}
catch (Exception)
{
return(-1);
}
};
return(result);
}
public static void Main()
{
RecurrenceFunction add = CreateRecurrence.primitiveRecurrence(
CreateRecurrence.projection(0),
CreateRecurrence.composition(
CreateRecurrence.projection(2),
CreateRecurrence.successor()));
System.Console.WriteLine(add(2, 3));
System.Console.WriteLine(add(20, 33));
System.Console.ReadKey();
}
