InitHEADmain

1 files changed, 151 insertions, 0 deletions

diff --git a/Homework/cs5300/project-three/parser/Item.java b/Homework/cs5300/project-three/parser/Item.java
new file mode 100644
index 0000000..1cdb134
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+++ b/Homework/cs5300/project-three/parser/Item.java
@@ -0,0 +1,151 @@
+/*
+ * To change this license header, choose License Headers in Project Properties.
+ * To change this template file, choose Tools | Templates
+ * and open the template in the editor.
+ */
+package parser;
+
+import java.util.ArrayList;
+import java.util.Objects;
+
+/**
+ * An LR(1) item.
+ *
+ */
+public class Item implements Comparable {
+
+  private Rule rule;
+  /**
+   * Position of the stack top in the production's RHS.
+   */
+  private int dot;
+  /**
+   * The lookahead symbol
+   */
+  private String a;
+
+  /**
+   * Creates a set of items given the rule and lookahead, one item per potential
+   * stack position placement. The number of item is the number of symbols on
+   * the rhs of the rule plus one.
+   *
+   * @param rule
+   * @param a
+   * @return
+   */
+  static ArrayList<Item> create(Rule rule, String a) {
+    ArrayList<Item> ret = new ArrayList<>();
+    final ArrayList<String> rhs = rule.getRhs();
+    for (int i = 0; i < rhs.size(); ++i) {
+      ret.add(new Item(rule, i, a));
+    }
+    ret.add(new Item(rule, rhs.size(), a));
+    return ret;
+  }
+
+  public Item(Rule rule, int dot, String a) {
+    this.rule = rule;
+    this.dot = dot;
+    this.a = a;
+  }
+
+  public Rule getRule() {
+    return rule;
+  }
+
+  public int getDot() {
+    return dot;
+  }
+
+  /**
+   * @return the lookahead symbol
+   */
+  public String getA() {
+    return a;
+  }
+
+  public String getLookahead() {
+    return getA();
+  }
+
+  /**
+   * Returns the symbol following the stack pointer. Returns null if the pointer
+   * is at the end of the rhs list.
+   *
+   * @return
+   */
+  public String getNextSymbol() {
+    if (dot < rule.getRhs().size()) {
+      return rule.getRhs().get(dot);
+    }
+    return null;
+  }
+
+  public String getNextNextSymbol() {
+    if (dot < rule.getRhs().size() - 1) {
+      return rule.getRhs().get(dot + 1);
+    }
+    return null;
+  }
+
+  public Item advance() {
+    return new Item(rule, dot + 1, a);
+  }
+
+  @Override
+  public int hashCode() {
+    int hash = 7;
+    hash = 37 * hash + Objects.hashCode(this.rule);
+    hash = 37 * hash + this.dot;
+    hash = 37 * hash + Objects.hashCode(this.a);
+    return hash;
+  }
+
+  @Override
+  public boolean equals(Object obj) {
+    if (obj == null) {
+      return false;
+    }
+    if (getClass() != obj.getClass()) {
+      return false;
+    }
+    final Item other = (Item) obj;
+    if (!Objects.equals(this.rule, other.rule)) {
+      return false;
+    }
+    if (this.dot != other.dot) {
+      return false;
+    }
+    if (!Objects.equals(this.a, other.a)) {
+      return false;
+    }
+    return true;
+  }
+
+  @Override
+  public String toString() {
+    String ret = "[" + rule.getLhs() + " -> ";
+    final ArrayList<String> rhs = rule.getRhs();
+    for (int i = 0; i < dot; ++i) {
+      ret += rhs.get(i) + " ";
+    }
+    ret += Character.toString((char) 0x25CF);
+    if (dot < rhs.size()) {
+      ret += " ";
+    }
+    for (int i = dot; i < rhs.size(); ++i) {
+      ret += rhs.get(i);
+      if (i < rhs.size() - 1) {
+        ret += " ";
+      }
+    }
+    ret += ", " + a + "]";
+    return ret;
+  }
+
+  @Override
+  public int compareTo(Object o) {
+    return toString().compareTo(o.toString());
+  }
+
+}