From c2ccf4e675c68d8b1cca6f662dbfbf800449247a Mon Sep 17 00:00:00 2001
From: Marcin Chrzanowski <marcin.j.chrzanowski@gmail.com>
Date: Mon, 21 Oct 2019 19:31:52 +0200
Subject: Intial commit - import scenario 2

---
 src/pl/edu/mimuw/cloudatlas/model/ValueNull.java | 155 +++++++++++++++++++++++
 1 file changed, 155 insertions(+)
 create mode 100644 src/pl/edu/mimuw/cloudatlas/model/ValueNull.java

(limited to 'src/pl/edu/mimuw/cloudatlas/model/ValueNull.java')

diff --git a/src/pl/edu/mimuw/cloudatlas/model/ValueNull.java b/src/pl/edu/mimuw/cloudatlas/model/ValueNull.java
new file mode 100644
index 0000000..e0c3f2a
--- /dev/null
+++ b/src/pl/edu/mimuw/cloudatlas/model/ValueNull.java
@@ -0,0 +1,155 @@
+/**
+ * Copyright (c) 2014, University of Warsaw
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without modification, are permitted
+ * provided that the following conditions are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright notice, this list of
+ * conditions and the following disclaimer.
+ *
+ * 2. Redistributions in binary form must reproduce the above copyright notice, this list of
+ * conditions and the following disclaimer in the documentation and/or other materials provided
+ * with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND ANY EXPRESS OR
+ * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND
+ * FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR
+ * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
+ * WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY
+ * WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+package pl.edu.mimuw.cloudatlas.model;
+
+import pl.edu.mimuw.cloudatlas.model.Value;
+import pl.edu.mimuw.cloudatlas.model.ValueNull;
+
+/**
+ * A special null value of an unknown type introduced to deal with nulls. This class is a singleton.
+ * 
+ * @see TypePrimitve#NULL
+ * @see Type#isCompatible(Value)
+ */
+public class ValueNull extends Value {
+	private static ValueNull instance = null;
+	
+	private ValueNull() {}
+	
+	/**
+	 * Gets a singleton instance of a <code>ValueNull</code> class. Every call to this method returns the same
+	 * reference.
+	 * 
+	 * @return an instance of <code>ValueNull</code>
+	 */
+	public static ValueNull getInstance() {
+		if(instance == null)
+			instance = new ValueNull();
+		return instance;
+	}
+	
+	@Override
+	public Value getDefaultValue() {
+		return instance;
+	}
+	
+	@Override
+	public Value convertTo(Type type) {
+		switch(type.getPrimaryType()) {
+			case STRING:
+				return ValueString.NULL_STRING;
+			default:
+				return this;
+		}
+	}
+	
+	@Override
+	public Type getType() {
+		return TypePrimitive.NULL;
+	}
+	
+	@Override
+	public boolean isNull() {
+		return true;
+	}
+	
+	@Override
+	public Value isEqual(Value value) {
+		return new ValueBoolean(isNull() && value.isNull());
+	}
+	
+	@Override
+	public Value isLowerThan(Value value) {
+		if(value == getInstance())
+			return this;
+		return value.isLowerThan(this);
+	}
+	
+	@Override
+	public Value addValue(Value value) {
+		if(value == getInstance())
+			return this;
+		return value.addValue(this);
+	}
+	
+	@Override
+	public Value subtract(Value value) {
+		if(value == getInstance())
+			return this;
+		return value.subtract(this);
+	}
+	
+	@Override
+	public Value multiply(Value value) {
+		if(value == getInstance())
+			return this;
+		return value.multiply(this);
+	}
+	
+	@Override
+	public Value divide(Value value) {
+		if(value == getInstance())
+			return this;
+		return value.divide(this);
+	}
+	
+	@Override
+	public Value modulo(Value value) {
+		if(value == getInstance())
+			return this;
+		return value.modulo(this);
+	}
+	
+	@Override
+	public Value and(Value value) {
+		if(value == getInstance())
+			return this;
+		return value.and(this);
+	}
+	
+	@Override
+	public Value or(Value value) {
+		if(value == getInstance())
+			return this;
+		return value.or(this);
+	}
+	
+	@Override
+	public Value regExpr(Value value) {
+		if(value == getInstance())
+			return this;
+		return value.regExpr(this);
+	}
+	
+	@Override
+	public Value negate() {
+		return this;
+	}
+	
+	@Override
+	public Value valueSize() {
+		return this;
+	}
+}
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