LinearMapper1d.h

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#ifndef NPSTAT_LINEARMAPPER1D_HH_
#define NPSTAT_LINEARMAPPER1D_HH_

#include "JetMETCorrections/InterpolationTables/interface/NpstatException.h"

namespace npstat {
  class LinearMapper1d {
  public:
    inline LinearMapper1d() : a_(1.0), b_(0.0) {}

    inline LinearMapper1d(const double x0, const double y0, const double x1, const double y1) {
      const double dx = x1 - x0;
      if (!dx)
        throw npstat::NpstatInvalidArgument(
            "In npstat::LinearMapper1d constructor: "
            "invalid arguments (x0 == x1)");
      a_ = (y1 - y0) / dx;
      b_ = ((y0 + y1) - a_ * (x0 + x1)) / 2.0;
    }

    inline LinearMapper1d(const double ca, const double cb) : a_(ca), b_(cb) {}

    inline double operator()(const double& x) const { return a_ * x + b_; }

    inline double a() const { return a_; }

    inline double b() const { return b_; }

    inline LinearMapper1d inverse() const {
      if (!a_)
        throw npstat::NpstatInvalidArgument(
            "In npstat::LinearMapper1d::inverse: "
            "mapping is not invertible");
      return LinearMapper1d(1.0 / a_, -b_ / a_);
    }

    inline LinearMapper1d operator*(const LinearMapper1d& r) const { return LinearMapper1d(a_ * r.a_, a_ * r.b_ + b_); }

  private:
    double a_;
    double b_;
  };
}  // namespace npstat

#endif  // NPSTAT_LINEARMAPPER1D_HH_