utlExprtk.h

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#ifndef __utlExprtk_h
#define __utlExprtk_h

#include "exprtk_lib.h"
#include <functional>
#include <vector>

namespace utl
{

template <class T=double>
inline std::function<T(T)> 
GetScalarFunctionFromString ( const std::string& funcStr )
{
  auto func = 
    [funcStr](T xval)
      {
      T x(xval);
      exprtk::symbol_table<T> symbol_table;
      symbol_table.add_variable("x",x);
      symbol_table.add_constants();

      exprtk::expression<T> expression;
      expression.register_symbol_table(symbol_table);

      exprtk::parser<T> parser;
      parser.compile(funcStr ,expression);

      T result = expression.value();
      return result;
      }; 
  return func;
}


template <class T=double>
inline std::function<T(std::vector<T>)> 
GetVectorFunctionFromString ( const std::string& funcStr )
{
  auto func = 
    [funcStr](const std::vector<T>& xval)
      {
      std::vector<T> x(xval);
      exprtk::symbol_table<T> symbol_table;
      symbol_table.add_vector("x",x);
      symbol_table.add_constants();

      exprtk::expression<T> expression;
      expression.register_symbol_table(symbol_table);

      exprtk::parser<T> parser;
      parser.compile(funcStr,expression);

      T result = expression.value();
      return result;
      }; 
  return func;
}

}

#endif