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Title: Structure

Description: None

Copyright (c) 1999 Steven J. Metsker.

Copyright (c) 2001 The Open For Business Project - www.ofbiz.org

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A Structure is a functor associated with a number of terms; a functor can be any object. A term is an object that implements the Term interface, including structures and variables.

An example of a structure is:

 starred(jamesCagney, "Yankee Doodle Dandy", Year)
 

This particular example has two elements that favor a parser: the quotes around the film title and the capitalization of the variable. When using Structure and Variable directly, you do not need the kinds of clues a parser needs. So, Yankee Doodle Dandy is just another string, whose internal blanks are not at all confusing. Further, a variable can have any string as its name, not necessarily capitalized.

You can create the starred example with

 Structure s = new Structure(
 "starred",
 new Term[]{
 new Structure("jamesCagney"),
 new Structure("Yankee Doodle Dandy"),
 new Variable("Year")});
 

Objects of this class, the superclass of all structures, should not appear in dynamic rules.

This constructor creates a list of two terms, regardless of the number of terms supplied here.

This allows construction of a list such as:

 Variable head = new Variable("Head");
 Variable tail = new Variable("Tail");
 Structure ht = Structure.list(new Term[] {head}, tail);
 

If two structures have equal functors and the same number of terms, they can unify if all of their terms unify.

This method dispatches the unify request to either a structure or a variable.

This method dispatches the unify request to the variable. Note that the variable may be instantiated to a structure that contains variables.

Note that a structure may contain variables or other structures as terms.

Objects of this class, the superclass of all structures, should not appear in dynamic rules. When a nondynamic rule creates its dynamic counterpart, it populates it with provable versions of its structures. A general Structure object will construct a ConsultingStructure when it participates in building a dynamic rule.

This particular method is almost never called. Subclasses implement more interesting behavior. false

This method accepts an array of terms and a tail, which must be a list structure or a variable. This method composes and returns a two-element array.

The first element of the returned array will always be the first element of the supplied terms array.

The second element of the returned array will be a list. This list will be a concatenation of the remainder of the given array with the supplied tail.

This constructor creates a list of two terms, regardless of the number of terms supplied here. The new list's first term is the first term of the supplied array. Its second term is a list of the remaining terms. Term[] the terms of the list

This allows construction of a list such as:

 Variable head = new Variable("Head");
 Variable tail = new Variable("Tail");
 Structure ht = Structure.list(new Term[] {head}, tail);
 

If two structures have equal functors and the same number of terms, they can unify if all of their terms unify. For example, the following structures can unify:

 address(Detail, city(City), state(State))
 address(mall(fayette), city(lexington), state(ky))
 

 Detail = mall(fayette),
 City = lexington,
 State = ky
 

This method dispatches the unify request to either a structure or a variable. The receiver will get a signature match from this object as a Structure, not just a Term.
Parameters:
  Term - a term to unify with the sum of the variables that bind to values to makethe unification work. Returns null if theunification fails.

This method dispatches the unify request to the variable. Note that the variable may be instantiated to a structure that contains variables. An uninstantiated variable will bind to this structure, but an instantiated variable will forward the unification request to its instantiation.
Parameters:
  Term - a term to unify with the sum of the variables that bind to values to makethe unification work. Returns null if theunification fails.

Note that a structure may contain variables or other structures as terms. This method adds this structure's variables directly to the returned unification. In addition, this method adds in all the variables from the structures among this structure's terms.

For example, the variables of:

 address(street(StreetName), city(CityName), State)