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Ingy döt Net 2013-10-27 22:24:23 +00:00
parent 6f050a029e
commit 776bba907c
3887 changed files with 59894 additions and 7280 deletions
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144
Task/Y-combinator/Java/y-combinator-3.java
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@ -1,142 +1,8 @@
import java.math.BigInteger;
import java.util.Arrays;
import java.util.ArrayList;
import java.util.Collections;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import java.util.function.Function;
interface Function<INPUT, OUTPUT> {
public static final List<Void> NIL = Collections.emptyList();
public OUTPUT call(List<? extends INPUT> input);
}
class Functions {
public static <OUTPUT> OUTPUT call(
Function<Void, OUTPUT> f) {
return f.call(Function.NIL);
}
public static <INPUT, OUTPUT> OUTPUT call(
Function<INPUT, OUTPUT> f,
INPUT input) {
return f.call(Collections.singletonList(input));
}
public static <INPUT, OUTPUT> OUTPUT call(
Function<INPUT, OUTPUT> f,
INPUT... input) {
return f.call(Arrays.asList(input));
}
public static <INPUT, OUTPUT> OUTPUT call(
Function<INPUT, OUTPUT> f,
Class<INPUT> type,
INPUT... input) {
List<INPUT> i = Collections.checkedList(new ArrayList<INPUT>(), type);
i.addAll(Arrays.asList(input));
return f.call(i);
}
public static <T> T input(
List<T> input, int index) {
return input.size() > index
? input.get(index)
: null;
}
public static <INPUT, INPUT_OUTPUT, OUTPUT> Function<INPUT, OUTPUT> compose(
final Function<INPUT_OUTPUT, OUTPUT> f
, final Function<INPUT, INPUT_OUTPUT> g) {
return new Function<INPUT, OUTPUT>() {
@Override
public OUTPUT call(List<? extends INPUT> input) {
return f.call(Collections.singletonList(g.call(input)));
}
};
}
public static <INPUT, OUTPUT> Function<INPUT, OUTPUT> y(
final Function<Function<INPUT, OUTPUT>, Function<INPUT, OUTPUT>> f) {
return new Function<INPUT, OUTPUT>() {
@Override
public OUTPUT call(List<? extends INPUT> input) {
return Functions.call(f, new Function<INPUT, OUTPUT>() {
@Override
public OUTPUT call(List<? extends INPUT> input) {
return y(f).call(input);
}
}).call(input);
}
};
}
}
public class Y {
public static BigInteger TWO = BigInteger.ONE.add(BigInteger.ONE);
public static void main(String[] args) {
Function<Number, Number> fibonacci = Functions.y(
new Function<Function<Number, Number>, Function<Number, Number>>() {
@Override
public Function<Number, Number> call(List<? extends Function<Number, Number>> input) {
final Function<Number, Number> f = Functions.input(input, 0);
return new Function<Number, Number>() {
@Override
public Number call(List<? extends Number> input) {
BigInteger n = new BigInteger(Functions.input(input, 0).toString());
if (n.compareTo(TWO) <= 0) return 1;
return new BigInteger(Functions.call(f, n.subtract(BigInteger.ONE)).toString())
.add(new BigInteger(Functions.call(f, n.subtract(TWO)).toString()));
}
};
}
}
);
Function<Number, Number> factorial = Functions.y(
new Function<Function<Number, Number>, Function<Number, Number>>() {
@Override
public Function<Number, Number> call(List<? extends Function<Number, Number>> input) {
final Function<Number, Number> f = Functions.input(input, 0);
return new Function<Number, Number>() {
@Override
public Number call(List<? extends Number> input) {
BigInteger n = new BigInteger(Functions.input(input, 0).toString());
if (n.compareTo(BigInteger.ONE) <= 0) return 1;
return n.multiply(
new BigInteger(Functions.call(f, n.subtract(BigInteger.ONE)).toString())
);
}
};
}
}
);
Function<Number, Number> ackermann = Functions.y(
new Function<Function<Number, Number>, Function<Number, Number>>() {
@Override
public Function<Number, Number> call(List<? extends Function<Number, Number>> input) {
final Function<Number, Number> f = Functions.input(input, 0);
return new Function<Number, Number>() {
@Override
public Number call(List<? extends Number> input) {
BigInteger m = new BigInteger(Functions.input(input, 0) + "");
BigInteger n = new BigInteger(Functions.input(input, 1) + "");
return m.equals(BigInteger.ZERO)
? n.add(BigInteger.ONE)
: Functions.call(f, m.subtract(BigInteger.ONE),
n.equals(BigInteger.ZERO)
? BigInteger.ONE
: Functions.call(f, m, n.subtract(BigInteger.ONE)));
}
};
}
}
);
System.out.println("fibonacci(10) = " + Functions.call(fibonacci, 10));
System.out.println("factorial(10) = " + Functions.call(factorial, 10));
System.out.println("ackermann(3, 7) = " + Functions.call(ackermann, 3, 7));
@FunctionalInterface
public interface SelfApplicable<OUTPUT> extends Function<SelfApplicable<OUTPUT>, OUTPUT> {
public default OUTPUT selfApply() {
return apply(this);
}
}