static void Main(params String[] arguments)
{
BigInteger TWO = BigInteger.One + BigInteger.One;
Func <IFormattable, long> toLong = x => long.Parse(x.ToString());
Func <IFormattable, BigInteger> toBigInteger = x => new BigInteger(toLong(x));
/* Based on https://gist.github.com/aruld/3965968/#comment-604392 */
Y <VarargsFunction <IFormattable, IFormattable> > combinator = y => f => x => f(y.selfApply()(f))(x);
FixedPoint <VarargsFunction <IFormattable, IFormattable> > fixedPoint =
combinator.Cast <SelfApplicable <FixedPoint <VarargsFunction <IFormattable, IFormattable> > > >().selfApply();
VarargsFunction <IFormattable, IFormattable> fibonacci = fixedPoint(
f => VarargsFunction.upgrade(
toBigInteger.andThen(
n => (IFormattable)(
(n.CompareTo(TWO) <= 0)
? 1
: BigInteger.Parse(f(n - BigInteger.One).ToString())
+ BigInteger.Parse(f(n - TWO).ToString()))
)
)
);
VarargsFunction <IFormattable, IFormattable> factorial = fixedPoint(
f => VarargsFunction.upgrade(
toBigInteger.andThen(
n => (IFormattable)((n.CompareTo(BigInteger.One) <= 0)
? 1
: n * BigInteger.Parse(f(n - BigInteger.One).ToString()))
)
)
);
VarargsFunction <IFormattable, IFormattable> ackermann = fixedPoint(
f => VarargsFunction.upgrade(
(BigInteger m, BigInteger n) => m.Equals(BigInteger.Zero)
? n + BigInteger.One
: f(
m - BigInteger.One,
n.Equals(BigInteger.Zero)
? BigInteger.One
: f(m, n - BigInteger.One)
)
).transformArguments(toBigInteger)
);
var functions = new Dictionary <String, VarargsFunction <IFormattable, IFormattable> >();
functions.Add("fibonacci", fibonacci);
functions.Add("factorial", factorial);
functions.Add("ackermann", ackermann);
var parameters = new Dictionary <VarargsFunction <IFormattable, IFormattable>, IFormattable[]>();
parameters.Add(functions["fibonacci"], new IFormattable[] { 20 });
parameters.Add(functions["factorial"], new IFormattable[] { 10 });
parameters.Add(functions["ackermann"], new IFormattable[] { 3, 2 });
functions.AsParallel().Select(
entry => entry.Key
+ "[" + String.Join(", ", parameters[entry.Value].Select(x => x.ToString())) + "]"
+ " = "
+ entry.Value(parameters[entry.Value])
).ForAll(Console.WriteLine);
}
public static VarargsFunction <PRE_INPUTS, OUTPUT> transformArguments <PRE_INPUTS, INPUTS, OUTPUT>(
this VarargsFunction <INPUTS, OUTPUT> @this,
Func <PRE_INPUTS, INPUTS> transformer)
{
return(inputs => @this(inputs.AsParallel().AsOrdered().Select(transformer).ToArray()));
}
public static Func <INPUTS, OUTPUT> toFunction <INPUTS, OUTPUT>(
this VarargsFunction <INPUTS, OUTPUT> @this)
{
return(input => @this(input));
}
public static Func <INPUTS, INPUTS, OUTPUT> toBiFunction <INPUTS, OUTPUT>(
this VarargsFunction <INPUTS, OUTPUT> @this)
{
return((input, input2) => @this(input, input2));
}
public static VarargsFunction <INPUTS, POST_OUTPUT> andThen <INPUTS, OUTPUT, POST_OUTPUT>(
this VarargsFunction <INPUTS, OUTPUT> @this,
VarargsFunction <OUTPUT, POST_OUTPUT> after)
{
return(inputs => after(@this(inputs)));
}
