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diff --git a/libsolidity/formal/SymbolicVariables.h b/libsolidity/formal/SymbolicVariables.h
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+/*
+	This file is part of solidity.
+
+	solidity 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 3 of the License, or
+	(at your option) any later version.
+
+	solidity 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 solidity.  If not, see <http://www.gnu.org/licenses/>.
+*/
+
+#pragma once
+
+#include <libsolidity/formal/SSAVariable.h>
+
+#include <libsolidity/formal/SolverInterface.h>
+
+#include <libsolidity/ast/Types.h>
+
+#include <memory>
+
+namespace dev
+{
+namespace solidity
+{
+
+class Type;
+
+/**
+ * This abstract class represents the symbolic version of a program variable.
+ */
+class SymbolicVariable
+{
+public:
+	SymbolicVariable(
+		TypePointer _type,
+		std::string const& _uniqueName,
+		smt::SolverInterface& _interface
+	);
+
+	virtual ~SymbolicVariable() = default;
+
+	smt::Expression currentValue() const
+	{
+		return valueAtIndex(m_ssa->index());
+	}
+
+	virtual smt::Expression valueAtIndex(int _index) const = 0;
+
+	smt::Expression increaseIndex()
+	{
+		++(*m_ssa);
+		return currentValue();
+	}
+
+	unsigned index() const { return m_ssa->index(); }
+	unsigned& index() { return m_ssa->index(); }
+
+	/// Sets the var to the default value of its type.
+	/// Inherited types must implement.
+	virtual void setZeroValue() = 0;
+	/// The unknown value is the full range of valid values.
+	/// It is sub-type dependent, but not mandatory.
+	virtual void setUnknownValue() {}
+
+protected:
+	std::string uniqueSymbol(unsigned _index) const;
+
+	TypePointer m_type = nullptr;
+	std::string m_uniqueName;
+	smt::SolverInterface& m_interface;
+	std::shared_ptr<SSAVariable> m_ssa = nullptr;
+};
+
+/**
+ * Specialization of SymbolicVariable for Bool
+ */
+class SymbolicBoolVariable: public SymbolicVariable
+{
+public:
+	SymbolicBoolVariable(
+		TypePointer _type,
+		std::string const& _uniqueName,
+		smt::SolverInterface& _interface
+	);
+
+	/// Sets the var to false.
+	void setZeroValue();
+	/// Does nothing since the SMT solver already knows the valid values for Bool.
+	void setUnknownValue();
+
+protected:
+	smt::Expression valueAtIndex(int _index) const;
+};
+
+/**
+ * Specialization of SymbolicVariable for Integers
+ */
+class SymbolicIntVariable: public SymbolicVariable
+{
+public:
+	SymbolicIntVariable(
+		TypePointer _type,
+		std::string const& _uniqueName,
+		smt::SolverInterface& _interface
+	);
+
+	/// Sets the var to 0.
+	void setZeroValue();
+	/// Sets the variable to the full valid value range.
+	void setUnknownValue();
+
+protected:
+	smt::Expression valueAtIndex(int _index) const;
+};
+
+/**
+ * Specialization of SymbolicVariable for Address
+ */
+class SymbolicAddressVariable: public SymbolicIntVariable
+{
+public:
+	SymbolicAddressVariable(
+		std::string const& _uniqueName,
+		smt::SolverInterface& _interface
+	);
+};
+
+/**
+ * Specialization of SymbolicVariable for FixedBytes
+ */
+class SymbolicFixedBytesVariable: public SymbolicIntVariable
+{
+public:
+	SymbolicFixedBytesVariable(
+		unsigned _numBytes,
+		std::string const& _uniqueName,
+		smt::SolverInterface& _interface
+	);
+};
+
+}
+}