123 lines
2.4 KiB
Java
123 lines
2.4 KiB
Java
/*
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* Name: Mike Cifelli
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* Course: CIS 443 - Programming Languages
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* Assignment: Lisp Parser
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*/
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package parser;
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/**
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* This is the base class for memory in the PL-Lisp implementation.
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*/
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public class SExpression {
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// for mark and sweep garbage collection
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private boolean marked = false;
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/**
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* Determine if this <code>SExpression</code> is marked.
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*
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* @return
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* <code>true</code> if this <code>SExpression</code> is marked;
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* <code>false</code> otherwise
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*/
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public final boolean isMarked() {
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return marked;
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}
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/**
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* Set the marked status of this S-expression to the specified value.
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*
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* @param value
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* the value to assign to this S-expression's marked status
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*/
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public final void setMarked(final boolean value) {
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marked = value;
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}
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// Lisp type predicates;
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// by default, all return false (an SExpression effectively has NO type);
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// overridden in subclasses to describe their Lisp type
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/**
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* Test if this S-expression is NULL.
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*
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* @return
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* <code>false</code>
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*/
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public boolean nullp() {
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return false;
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}
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/**
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* Test if this S-expression is an ATOM.
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*
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* @return
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* <code>false</code>
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*/
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public boolean atomp() {
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return false;
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}
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/**
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* Test if this S-expression is a CONS cell.
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*
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* @return
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* <code>false</code>
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*/
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public boolean consp() {
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return false;
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}
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/**
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* Test if this S-expression is a LIST.
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*
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* @return
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* the value of <code>(consp() || nullp())</code>
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*/
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public boolean listp() {
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return (consp() || nullp());
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}
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/**
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* Test if this S-expression is a NUMBER.
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*
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* @return
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* <code>false</code>
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*/
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public boolean numberp() {
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return false;
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}
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/**
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* Test if this S-expression is a SYMBOL.
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*
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* @return
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* <code>false</code>
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*/
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public boolean symbolp() {
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return false;
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}
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/**
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* Test if this S-expression is a FUNCTION.
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*
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* @return
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* <code>false</code>
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*/
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public boolean functionp() {
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return false;
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}
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/**
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* Test if this S-expression is a STRING.
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*
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* @return
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* <code>false</code>
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*/
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public boolean stringp() {
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return false;
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}
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}
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