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78 lines
2.3 KiB
78 lines
2.3 KiB
//==============================================================================
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//
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// Copyright (c) 2002-
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// Authors:
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// * Dave Parker <david.parker@comlab.ox.ac.uk> (University of Oxford)
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//
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//------------------------------------------------------------------------------
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//
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// This file is part of PRISM.
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//
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// PRISM is free software; you can redistribute it and/or modify
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// it under the terms of the GNU General Public License as published by
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// the Free Software Foundation; either version 2 of the License, or
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// (at your option) any later version.
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//
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// PRISM is distributed in the hope that it will be useful,
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// but WITHOUT ANY WARRANTY; without even the implied warranty of
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// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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// GNU General Public License for more details.
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//
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// You should have received a copy of the GNU General Public License
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// along with PRISM; if not, write to the Free Software Foundation,
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// Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
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//
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//==============================================================================
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package simulator.sampler;
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import simulator.*;
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import prism.*;
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import parser.ast.*;
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public class SamplerNext extends SamplerBoolean
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{
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private Expression target;
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/**
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* Construct a sampler for a "next" property.
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* Passed in ExpressionTemporal should be a property of this type.
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* All constants should have already been evaluated/replaced.
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*/
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public SamplerNext(ExpressionTemporal expr) throws PrismException
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{
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// Make sure expression is of the correct type
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// Then extract other required info
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if (expr.getOperator() != ExpressionTemporal.P_X)
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throw new PrismException("Error creating Sampler");
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target = expr.getOperand2();
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// Initialise sampler info
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reset();
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resetStats();
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}
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@Override
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public boolean update(Path path, ModelGenerator modelGen) throws PrismException
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{
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// If the answer is already known we should do nothing
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if (valueKnown)
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return true;
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// X "target" is true iff state 1 satisfies "target"
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if (path.size() == 1) {
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valueKnown = true;
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value = target.evaluateBoolean(path.getCurrentState());
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}
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// Nothing else to do: if path size is 0, can't decide;
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// if path size > 1 (should never happen), nothing changes
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return valueKnown;
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}
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@Override
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public boolean needsBoundedNumSteps()
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{
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// Always bounded
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return true;
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}
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}
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