VariableFormulaConstructor.h

#include <analysis/VariableManager/Manager.h>
#include <framework/utilities/FormulaParser.h>
 
namespace Belle2 {
  struct VariableFormulaConstructor {
    typedef Variable::Manager::FunctionPtr type;
    typedef FormulaParserBase::EOperator Op;
    type operator()(const std::string& name)
    {
      auto var = Variable::Manager::Instance().getVariable(name);
      if (!var) throw std::runtime_error("Could not find " + name + " via the Variable::Manager. Check the name");
      return var->function;
    }
 
    type operator()(double value)
    {
      return [value](const Particle*) { return value; };
    }
 
    type operator()(Op op, const type& a, const type& b)
    {
      return [op, a, b](const Particle * p) {
        switch (op) {
          case Op::c_plus: return a(p) + b(p);
          case Op::c_minus: return a(p) - b(p);
          case Op::c_multiply: return a(p) * b(p);
          case Op::c_divide: return a(p) / b(p);
          case Op::c_power: return std::pow(a(p), b(p));
          default: break;
        }
        throw std::runtime_error("Cannot handle operator " + std::to_string((int)op));
      };
    }
 
    type operator()(Op op, double& a, const type& b)
    {
      return [op, a, b](const Particle * p) {
        switch (op) {
          case Op::c_plus: return a + b(p);
          case Op::c_minus: return a - b(p);
          case Op::c_multiply: return a * b(p);
          case Op::c_divide: return a / b(p);
          case Op::c_power: return std::pow(a, b(p));
          default: break;
        }
        throw std::runtime_error("Cannot handle operator " + std::to_string((int)op));
      };
    }
 
    type operator()(Op op, const type& a, double b)
    {
      return [op, a, b](const Particle * p) {
        switch (op) {
          case Op::c_plus: return a(p) + b;
          case Op::c_minus: return a(p) - b;
          case Op::c_multiply: return a(p) * b;
          case Op::c_divide: return a(p) / b;
          case Op::c_power: return std::pow(a(p), b);
          default: break;
        }
        throw std::runtime_error("Cannot handle operator " + std::to_string((int)op));
      };
    }
  };
}