Replace home-grown iterators and map entries with proper types

Author: Steffen Märcker

prism/src/explicit/DTMCEmbeddedSimple.java

@@ -27,6 +27,7 @@
 package explicit;
 
 import java.util.*;
+import java.util.AbstractMap.SimpleImmutableEntry;
 import java.util.Map.Entry;
 
 import explicit.rewards.MCRewards;
@@ -214,12 +215,11 @@ public Iterator<Entry<Integer,Double>> getTransitionsIterator(int s)
 	{
 		if (exitRates[s] == 0) {
 			// return prob-1 self-loop
-			return Collections.singletonMap(s, 1.0).entrySet().iterator();
+			return DiracDistribution.iterator(s);
 		} else {
-			final Iterator<Entry<Integer,Double>> ctmcIterator = ctmc.getTransitionsIterator(s);
-			
+			Iterator<Entry<Integer,Double>> ctmcIterator = ctmc.getTransitionsIterator(s);
 			// return iterator over entries, with probabilities divided by exitRates[s]
-			final double er = exitRates[s];
+			double er = exitRates[s];
 			return new Iterator<Entry<Integer,Double>>() {
 				@Override
 				public boolean hasNext()
@@ -230,27 +230,10 @@ public boolean hasNext()
 				@Override
 				public Entry<Integer, Double> next()
 				{
-					final Entry<Integer, Double> ctmcEntry = ctmcIterator.next();
-					
-					return new Entry<Integer, Double>() {
-						@Override
-						public Integer getKey()
-						{
-							return ctmcEntry.getKey();
-						}
-
-						@Override
-						public Double getValue()
-						{
-							return ctmcEntry.getValue() / er;
-						}
-
-						@Override
-						public Double setValue(Double value)
-						{
-							throw new UnsupportedOperationException();
-						}
-					};
+					Entry<Integer, Double> transition = ctmcIterator.next();
+					Integer state = transition.getKey();
+					double probability = transition.getValue() / er;
+					return new SimpleImmutableEntry<>(state, probability);
 				}
 			};
 		}
@@ -259,7 +242,7 @@ public Double setValue(Double value)
 	@Override
 	public void forEachTransition(int s, TransitionConsumer c)
 	{
-		final double er = exitRates[s];
+		double er = exitRates[s];
 		if (er == 0) {
 			// exit rate = 0 -> prob 1 self loop
 			c.accept(s, s, 1.0);

prism/src/explicit/DiracDistribution.java

@@ -0,0 +1,81 @@
+//==============================================================================
+//	
+//	Copyright (c) 2019-
+//	Authors:
+//	* Steffen Maercker <steffen.maercker@tu-dresden.de> (TU Dresden)
+//	
+//------------------------------------------------------------------------------
+//	
+//	This file is part of PRISM.
+//	
+//	PRISM is free software; you can redistribute it and/or modify
+//	it under the terms of the GNU General Public License as published by
+//	the Free Software Foundation; either version 2 of the License, or
+//	(at your option) any later version.
+//	
+//	PRISM is distributed in the hope that it will be useful,
+//	but WITHOUT ANY WARRANTY; without even the implied warranty of
+//	MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+//	GNU General Public License for more details.
+//	
+//	You should have received a copy of the GNU General Public License
+//	along with PRISM; if not, write to the Free Software Foundation,
+//	Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
+//	
+//==============================================================================
+
+package explicit;
+
+import java.util.Iterator;
+import java.util.Map;
+import java.util.Map.Entry;
+
+import common.iterable.SingletonIterator;
+
+public class DiracDistribution implements Iterable<Entry<Integer, Double>>
+{
+	private final Entry<Integer, Double> transition;
+
+	public DiracDistribution(final int state)
+	{
+		this.transition = new Transition(state);
+	}
+
+	public Iterator<Entry<Integer, Double>> iterator()
+	{
+		return new SingletonIterator.Of<>(transition);
+	}
+
+	public static Iterator<Entry<Integer, Double>> iterator(final int state)
+	{
+		return new SingletonIterator.Of<>((Entry<Integer, Double>) new Transition(state));
+	}
+
+	public static class Transition implements Map.Entry<Integer, Double>
+	{
+		private final Integer state;
+
+		public Transition(final int state)
+		{
+			this.state = state;
+		}
+
+		@Override
+		public Integer getKey()
+		{
+			return state;
+		}
+
+		@Override
+		public Double getValue()
+		{
+			return 1.0;
+		}
+
+		@Override
+		public Double setValue(final Double value)
+		{
+			throw new UnsupportedOperationException("immutable entry");
+		}
+	}
+}