Function.html

Function.java

/*
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package blog;
import java.util.*;
import common.Util;
import common.TupleIterator;

Represents a BLOG function. A function is specified by its name, return type, and argument types.



public abstract class Function {
    public Function( String fname, List argTypeList, Type retType ){
	sig = new Sig(fname, argTypeList);
	this.retType = retType;
    }

    public String getName() {
	return sig.getName();
    }

    public Type[] getArgTypes() {
	return sig.getArgTypes();
    }

    public Type getRetType() {
	return retType;
    }

    public Function.Sig getSig() {
	return sig;
    }

Returns true if this function applies to all tuples of objects with the given types. This is true if each type in the given tuple is a subtype of the corresponding type in this function's argument type tuple (and the tuples have the same length).


    public boolean appliesTo(Type[] types) {
	if (types.length != sig.getArgTypes().length) { 
	    return false;
	}

	for (int i = 0; i < types.length; ++i) {
	    if (!types[i].isSubtypeOf(sig.getArgTypes()[i])) {
		return false;
	    }
	}

	return true;
    }

Returns true if this function could apply to some tuple of non-null objects with the given types. Since we have single inheritance (except for NULL_TYPE), this is true if every type in the given tuple is either a subtype or a supertype of the corresponding type in this function's argument type tuple (and the tuples have the same length).


    public boolean overlapsWith(Type[] types) {
	if (types.length != sig.getArgTypes().length) {
	    return false;
	}

	for (int i = 0; i < types.length; ++i) {
	    if (!(types[i].isSubtypeOf(sig.getArgTypes()[i])
		  || sig.getArgTypes()[i].isSubtypeOf(types[i]))) {
		return false;
	    }
	}

	return true;
    }

Returns true if the dependency statement or interpretation statement for this function (if any) satisfies type and scope constraints. If there is a type or scope error, prints a message to standard error and returns false.

This default implementation just returns true.


    public boolean checkTypesAndScope(Model model) {
	return true;
    }

Ensures that this function is ready to be used by an inference engine. If any errors occur, prints a message to standard error. Returns the number of errors that occurred.

This default implementation just returns 0. of this method invocation. Ordered by invocation order. Used to detect cycles.

Parameters:

callStack - Set of objects whose compile methods are parents


    public int compile(LinkedHashSet callStack) {
	return 0;
    }

Returns the value of this function applied to the given tuple of arguments in the given partial world. If the given partial world is not complete enough to determine the function value, this method returns null.


    public Object getValue(Object[] args, PartialWorld w) {
	return getValueInContext(args, new DefaultEvalContext(w), false);
    }

Returns the value of this function applied to an empty tuple of arguments in the given partial world (this method should be used only for zero-ary functions). If the given partial world is not complete enough to determine the function value, this method returns null.


    public Object getValue(PartialWorld w) {
	return getValueInContext(new Object[0], new DefaultEvalContext(w), 
				 true);
    }

Returns the value of this function applied to the given single argument in the given partial world (this method should be used only for unary functions). If the given partial world is not complete enough to determine the function value, this method returns null.


    public Object getValueSingleArg(Object arg, PartialWorld w) {
	Object[] args = {arg};
	return getValueInContext(args, new DefaultEvalContext(w), true);
    }

Returns the value of this function applied to the given pair of arguments in the given partial world (this method should be used only for binary functions). If the given partial world is not complete enough to determine the function value, this method returns null.


    public Object getValue(Object arg1, Object arg2, PartialWorld w) {
	Object[] args = {arg1, arg2};
	return getValueInContext(args, new DefaultEvalContext(w), true);
    }

Returns the value of this function applied to the given tuple of arguments in the given context. If the partial world in the given context is not complete enough to determine the function value, this method returns null. args array will not be modified

Parameters:

stable - if true, the caller guarantees that the


    public abstract Object getValueInContext(Object[] args, 
					     EvalContext context, 
					     boolean stable);

Returns the value of this function on arguments that are not in its domain. This is Boolean.FALSE for Boolean functions, and Model.NULL for other functions.


    public Object getDefaultValue() {
	return retType.getDefaultValue();
    }

Returns true if this function is indexed by time, that is, it has a final argument of type Timestep.


    public boolean isTimeIndexed() {
	return ((sig.argTypes.length > 0)
		&& (sig.argTypes[sig.argTypes.length - 1]
		    == BuiltInTypes.TIMESTEP));
    }

Returns an iterator over the tuples of objects that can serve as arguments to this function. Raises a fatal error if this would require enumerating a random or infinite set.

Returns: Iterator over Lists


    public Iterator domainIterator() {
	return domainIterator(false);
    }

Returns an iterator over the tuples of objects that can serve as arguments to this function. Raises a fatal error if this would require enumerating a random or infinite set. tuples (useful for time-indexed functions)

Returns: Iterator over Lists

Parameters:

skipLastArg - if true, exclude the last argument from the


    public Iterator domainIterator(boolean skipLastArg) {
	List argDomains = new ArrayList();
	int numDomains = (skipLastArg ? 
			  sig.argTypes.length - 1 : sig.argTypes.length);
	for (int i = 0; i < numDomains; ++i) {
	    Type t = sig.argTypes[i];
	    if (t.hasFiniteGuaranteed() && t.getPOPs().isEmpty()) {
		argDomains.add(t.getGuaranteedObjects());
	    } else {
		Util.fatalError("Can't enumerate set of objects of type " + t
				+ " because this set is random or infinite");
	    }
	}

	return new TupleIterator(argDomains);
    }

Returns an index indicating when this function was declared (or otherwise created).


    public int getCreationIndex() {
	return creationIndex;
    }

Returns this function's name.


    public String toString() {
	return sig.getName();
    }

Nested class representing a function signature, that is, a function name and a tuple of argument types.


    public static class Sig {

Creates a signature for a zero-ary function with the given name.


	public Sig(String name) {
	    this.name = name;
	    argTypes = NO_ARG_TYPES;
	}

Creates a signature for a function with the given name and argument types.


        public Sig(String name, Type... types) {
            this.name = name;
            argTypes = types;
        }

Creates a signature for a function with the given name and argument types.

Parameters:

argTypeList - a List of Type objects


	public Sig(String name, List<Type> argTypeList) {
	    this.name = name;
	    argTypes = new Type[argTypeList.size()];
	    argTypeList.toArray(argTypes);
	}

	public String getName() {
	    return name;
	}

	public Type[] getArgTypes() {
	    return argTypes;
	}

	public boolean equals(Object o) {
	    if (o instanceof Function.Sig) {
		Function.Sig other = (Function.Sig) o;
		return ((name.equals(other.getName()))
			&& Arrays.equals(argTypes, other.getArgTypes()));
	    }
	    return false;
	}

	public int hashCode() {
	    int code = name.hashCode();
	    for (int i = 0; i < argTypes.length; ++i) {
		code ^= argTypes[i].hashCode();
	    }
	    return code;
	}

	public String toString() {
	    StringBuffer buf = new StringBuffer();
	    buf.append(name);
	    buf.append('(');
	    for (int i = 0; i < argTypes.length; ++i) {
		buf.append(argTypes[i]);
		if (i + 1 < argTypes.length) {
		    buf.append(", ");
		}
	    }
	    buf.append(')');

	    return buf.toString();
	}

	public String name;
	public Type[] argTypes;

	private static Type[] NO_ARG_TYPES = new Type[0];
    }

    private Function.Sig sig;
    private Type retType;

    private int creationIndex = Model.nextCreationIndex();
}

This file was generated on Tue Jun 08 17:53:36 PDT 2010 from file Function.java
by the ilog.language.tools.Hilite Java tool written by Hassan Aït-Kaci