Added a formula evaluator to replace TFormula calls

CommonTools/Utils/interface/FormulaEvaluator.h

@@ -0,0 +1,81 @@
+#ifndef CommonTools_Utils_FormulaEvaluator_h
+#define CommonTools_Utils_FormulaEvaluator_h
+// -*- C++ -*-
+//
+// Package:     CommonTools/Utils
+// Class  :     FormulaEvaluator
+// 
+/**\class FormulaEvaluator FormulaEvaluator.h "CommonTools/Utils/interface/FormulaEvaluator.h"
+
+ Description: [one line class summary]
+
+ Usage:
+    <usage>
+
+*/
+//
+// Original Author:  Christopher Jones
+//         Created:  Wed, 23 Sep 2015 21:12:11 GMT
+//
+
+// system include files
+#include <array>
+#include <vector>
+#include <memory>
+
+// user include files
+
+// forward declarations
+namespace reco {
+  namespace formula {
+    class EvaluatorBase;
+    inline double const* startingAddress(std::vector<double> const& iV) {
+      if(iV.empty()) {
+        return nullptr;
+      }
+      return &iV[0];
+    }
+
+    template<size_t t>
+      inline double const* startingAddress(std::array<double,t> const& iV) {
+      if(iV.empty()) {
+        return nullptr;
+      }
+      return &iV[0];
+    }
+
+  }
+
+  class FormulaEvaluator
+  {
+
+  public:
+    explicit FormulaEvaluator(std::string const& iFormula);
+
+    template<typename V, typename P>
+      double evaluate( V const& iVariables, P const& iParameters) const {
+      if (m_nVariables > iVariables.size()) {
+        throwWrongNumberOfVariables(iVariables.size());
+      }
+      if (m_nParameters > iParameters.size()) {
+        throwWrongNumberOfParameters(iParameters.size());
+      }
+      return evaluate( formula::startingAddress(iVariables),
+                       formula::startingAddress(iParameters));
+    }
+    // ---------- const member functions ---------------------
+
+  private:
+    double evaluate(double const* iVariables, double const* iParameters) const;
+
+    void throwWrongNumberOfVariables(size_t) const ;
+    void throwWrongNumberOfParameters(size_t) const;
+
+    std::shared_ptr<formula::EvaluatorBase const> m_evaluator; 
+    unsigned int m_nVariables = 0;
+    unsigned int m_nParameters = 0;
+
+};
+}
+
+#endif