YODA/Utils/Predicates.h

0001 // -*- C++ -*-
0002 //
0003 // This file is part of YODA -- Yet more Objects for Data Analysis
0004 // Copyright (C) 2008-2024 The YODA collaboration (see AUTHORS for details)
0005 //
0006 #ifndef YODA_PREDICATES_H
0007 #define YODA_PREDICATES_H
0008
0009 #include <iostream>
0010
0011 namespace YODA {
0012
0013
0014   /// @brief Functor to compare two floating point numbers and return whether they are fuzzily equivalent
0015   ///
0016   /// The equivalence comparison is of the form dev = |b-a|/refscale. The @a
0017   /// refscale argument may used to force the reference scale in this, otherwise
0018   /// (or if explicitly set to zero) it will default to (|a| + |b|)/2. The
0019   /// returned boolean is determined by the comparison |dev| < tol.
0020   struct CmpFloats {
0021     CmpFloats(double tol=1e-3, double refscale=0.0) : _tol(tol), _refscale(refscale) {}
0022     bool operator () (const double& a, const double& b) {
0023       const double div = (_refscale == 0) ? 0.5*(std::abs(a)+std::abs(b)) : _refscale;
0024       const double dev = (b-a)/div;
0025       // std::cout << "CmpFloats: " << a << " vs. " << b << " -> dev = " << dev << std::endl;
0026       return std::abs(dev) < _tol;
0027     }
0028     double _tol, _refscale;
0029   };
0030
0031
0032 }
0033
0034 #endif