mirror of https://github.com/DanilaFe/abacus
81 lines
1.9 KiB
Java
81 lines
1.9 KiB
Java
package org.nwapw.abacus.lexing.pattern;
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/**
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* A chain of nodes that can be treated as a single unit.
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* Used during pattern compilation.
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*
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* @param <T> the type used to identify which pattern has been matched.
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*/
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public class PatternChain<T> {
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/**
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* The head node of the chain.
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*/
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public PatternNode<T> head;
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/**
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* The tail node of the chain.
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*/
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public PatternNode<T> tail;
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/**
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* Creates a new chain with the given start and end.
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*
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* @param head the start of the chain.
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* @param tail the end of the chain.
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*/
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public PatternChain(PatternNode<T> head, PatternNode<T> tail) {
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this.head = head;
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this.tail = tail;
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}
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/**
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* Creates a chain that starts and ends with the same node.
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*
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* @param node the node to use.
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*/
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public PatternChain(PatternNode<T> node) {
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this(node, node);
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}
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/**
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* Creates an empty chain.
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*/
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public PatternChain() {
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this(null);
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}
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/**
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* Appends the other chain to this one. This modifies
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* the nodes, as well.
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* If this chain is empty, it is set to the other.
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*
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* @param other the other chain to append.
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*/
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public void append(PatternChain<T> other) {
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if (other.head == null || tail == null) {
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this.head = other.head;
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this.tail = other.tail;
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} else {
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tail.outputStates.add(other.head);
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tail = other.tail;
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}
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}
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/**
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* Appends a single node to this chain. This modifies
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* the nodes, as well.
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* If this chain is empty, it is set to the node.
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*
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* @param node the node to append to this chain.
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*/
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public void append(PatternNode<T> node) {
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if (tail == null) {
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head = tail = node;
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} else {
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tail.outputStates.add(node);
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tail = node;
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}
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}
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}
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