normalizedPhi.h

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#ifndef Math_notmalizedPhi_h
#define Math_notmalizedPhi_h
#include "DataFormats/Math/interface/deltaPhi.h"
#include <algorithm>

// return a value of phi into interval [-pi,+pi]
template<typename T>
constexpr
T normalizedPhi(T phi) { return reco::reduceRange(phi);}

// cernlib V306
template<typename T>
constexpr 
T proxim(T b, T a) {
        constexpr T c1 = 2.*M_PI;
        constexpr T c2 = 1/c1;
        return b+c1*std::round(c2*(a-b));
}

#include<iostream>

// smallest range
template<typename T>
constexpr
bool checkPhiInSymRange(T phi, T phi1, T phi2, float maxDphi=float(M_PI)) {
  // symmetrize
  if (phi2<phi1) std::swap(phi1,phi2);
  return checkPhiInRange(phi,phi1,phi2,maxDphi);
}

// counterclock-wise range
template<typename T>
constexpr
bool checkPhiInRange(T phi, T phi1, T phi2, float maxDphi=float(M_PI)) {
    phi2 = proxim(phi2,phi1);
    constexpr float c1 = 2.*M_PI;
    if (phi2<phi1) phi2+=c1;
    auto dphi = std::min(maxDphi,0.5f*(phi2-phi1));
    auto phiA = phi1+dphi;
    phi = proxim(phi,phiA);
    return std::abs(phiA-phi)<dphi;

    /* old "alternative algo"
    constexpr T c1 = 2.*M_PI;
    phi1 = normalizedPhi(phi1);
    phi2 = proxim(phi2,phi1);
    if (phi2<phi1) phi2+=c1;
    // phi & phi1 are in [-pi,pi] range...
    return ( (phi1 <= phi) & (phi <= phi2) )
//           || ( (phi1 <= phi-c1) & (phi-c1 <= phi2) )
           || ( (phi1 <= phi+c1) & (phi+c1 <= phi2) );
    */
}

#endif