parser.visitor.ExpressionTraverseNonNested: Helper for traversing Expressions without recursing into nested P/R/SS formulas

git-svn-id: https://www.prismmodelchecker.org/svn/prism/prism/trunk@11035 bbc10eb1-c90d-0410-af57-cb519fbb1720

prism/src/parser/visitor/ExpressionTraverseNonNested.java

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+//==============================================================================
+//	
+//	Copyright (c) 2015-
+//	Authors:
+//	* Joachim Klein <klein@tcs.inf.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 parser.visitor;
+
+import parser.ast.ExpressionProb;
+import parser.ast.ExpressionReward;
+import parser.ast.ExpressionSS;
+import prism.PrismLangException;
+
+/**
+ * Base class for recursively traversing an Expression, but not
+ * entering nested P/R/SS subexpressions.
+ *
+ * By default, will not recurse into the P/R/SS elements, but
+ * can be configured to allow a certain amount of nested P/R/SS
+ * elements before stopping.
+ *
+ * <br/>
+ * Subclasses should not override<br/>
+ * <ul>
+ *  <li>{@code visit(ExpressionProb)}</li>
+ *  <li>{@code visit(ExpressionReward)}</li>
+ *  <li>{@code visit(ExpressionSS)}</li>
+ * </ul>
+ */
+public class ExpressionTraverseNonNested extends ASTTraverse
+{
+	/** the current nesting level */
+	private int currentNesting;
+	/** the maximal nesting level that still allows recursion */
+	private int nestingLimit;
+
+	/** Constructor, defaulting to "no nesting" */
+	public ExpressionTraverseNonNested()
+	{
+		this(0);
+	}
+
+	/** Constructor, with "stop recursion after {@code nestingLimit} nestings" */
+	public ExpressionTraverseNonNested(int nestingLimit)
+	{
+		currentNesting = 0;
+		this.nestingLimit = 0;
+	}
+
+	/** Are we still allowed to recurse? */
+	private boolean inLimit()
+	{
+		return currentNesting <= nestingLimit;
+	}
+
+	@Override
+	public Object visit(ExpressionProb e) throws PrismLangException
+	{
+		currentNesting++;
+		// only visit if we are still in limit
+		if (!inLimit()) {
+			currentNesting--;
+			return null;
+		}
+		Object rv = super.visit(e);
+		currentNesting--;
+		return rv;
+	}
+
+	@Override
+	public Object visit(ExpressionReward e) throws PrismLangException
+	{
+		currentNesting++;
+		// only visit if we are still in limit
+		if (!inLimit()) {
+			currentNesting--;
+			return null;
+		}
+		Object rv = super.visit(e);
+		currentNesting--;
+		return rv;
+	}
+
+	@Override
+	public Object visit(ExpressionSS e) throws PrismLangException
+	{
+		currentNesting++;
+		// only visit if we are still in limit
+		if (!inLimit()) {
+			currentNesting--;
+			return null;
+		}
+		Object rv = super.visit(e);
+		currentNesting--;
+		return rv;
+	}
+}