scranton.list
Interface RecursiveList

All Known Implementing Classes:

RecursiveListViaLinear1Ind

public interface RecursiveList

A Java interface that parallels lists as defined by John McCarthy in LISP, a list is either empty or it is an ordered pair (head, Tail) where "head" is the object in the list and "Tail" is a, possibly empty, list (sublist).

Specifications:

A RecursiveList is

• empty, L=()
• or L = (h, T), where h is an object called the head and T is a, possibly empty, RecursiveList, called the tail

Initial Value:

L = ()

Method Summary

java.lang.Object	headOf() Returns reference to the Object at the head of the list.
void	insert(RecursiveList L) Replaces the current list with a new list composed by concatenating the current list to the list in the parameter, this = L+this.
boolean	isEmpty() Returns true if the current list is empty.
RecursiveList	remove() If this = (h, T), remove the current list and replace it by its tail, this' = T, return (h, ()).
RecursiveList	tailOf() Returns reference to the tail of the current list.
java.lang.String	toString() Returns a string representation of the list.

Method Detail

isEmpty

public boolean isEmpty()

Returns true if the current list is empty.

Specifications:

Returns this==()?

Returns:

this==()

headOf

public java.lang.Object headOf()

Returns reference to the Object at the head of the list.

Specifications:

this!=() this' = this = (h,T)
Returns h

Timing:

O(constant)

Returns:

Object Head of the list.

Throws:

assertion - error when this == ().

tailOf

public RecursiveList tailOf()

Returns reference to the tail of the current list.

Specifications:

this!=() this' = this = (h,T)

Timing:

O(constant)

Returns:

RecursiveList Returns reference to the tail of the current list.

Throws:

Assertion - When this==().

insert

public void insert(RecursiveList L)

Replaces the current list with a new list composed by concatenating the current list to the list in the parameter, this = L+this.

Specifications:

this'= L + this

Parameters:

L - List that will be prepended to this.

remove

public RecursiveList remove()

If this = (h, T), remove the current list and replace it by its tail, this' = T, return (h, ()).

Specifications:

this!=() this=(h,T)
this'=T
Return (h, ())

Timing:

O(constant)

Returns:

RecursiveList Returns the tail of the current list.

Throws:

Assertion - when this==().

toString

public java.lang.String toString()

Returns a string representation of the list. Returns the string representation, "[head \t tail]" or "[]" is the list is empty.

Returns:

RecursiveList empty list object from the implementing class