class PBatch: public TObject

 Batch commands for particle and value operations

 This class allows for particle operations for
 analysing angles, masses, or making boost and
 rotations of TLorentzVectors/PParticles

 It is used for the PProjector to make histograms
 _inside_ the event loop without the need of an
 analysis macro

 The syntax is inspired by C++, but only a few
 rules of C++ have been implemented. Furthermore, the syntax
 has been simplified to make it more readable, and an interface
 to the particle input (and maybe to the database in a later step)
 has been foreseen

 As usual we have assignments, operators, functions and methods
 Each operation can be seperated by a semicolon (;)

 A simple case is outlined in the following command
 _x = [p,1]->M();
 This means that the double _x (which is automatically constructed)
 is assigned to the mass of the particle [p,1]
 Particle in brackets are the only allowed use without instantiantion
 as they are (hopefully) filled by the input. The additional number
 can be used for ordering information

 + and - operation
 This adds/subtracts PParticles or doubles:
 pp = [p,1] + [p,2];
 ...nothing else then the pp composite
 _x = pp->M();
 gives the invariant mass of the pp pair
 CAVEAT: Do _not_ use object name which are
 already assigned to particles in the data base, e.g.
 pi0=[pi0] is not allowed, use _pi0=[pi0] instead

 Brackets: Objects can be nested:
 _x = ([p,1] + [p,2])->M();
 ...makes the same as the 2 lines above

 Build-in methods:
 M()              : Invariant mass of the object
 M2()             : Invariant mass^2 of the object
 Boost(obj)       : Boost into rest frame of "obj"
   Example:
   pp = p1->Boost([p,1] + [p,2]);
   ...boost p1 in the rest frame of [p,1]+[p,2]
 Rot(obj)         : Rotate object such that obj
                    would point to z-Direction
 Angle(obj)       : Opening angle between obj
 Theta()          : Theta of momentum
 Print()          : Dump 4momentum or double

 In addition, all browsable methods of the class PParticle
 can be used (functions without arguments)

 Example:
 obj->Px();

 Build-in functions:
 cos()
 fabs()

 In addition, the TFormula syntax can be used

 Example:
 val_new = (val + 1.2);
 val = (val * TMath::Pi());

 Conditions:
 if(arg)          : Interrupts the current chain if arg == 0

 A very complex example: Look for the helicity distribution
 of the e+e- pair in the eta Dalitz decay
 _eta=[eta]; _ep=[e+]; _em=[e-];
 _eta->Boost([p + p]); _em->Boost([p + p]); _ep->Boost([p + p]);
 _ep->Rot(_eta); _em->Rot(_eta); _eta->Rot(_eta) ;
 _ep->Boost(_eta); _em->Boost(_eta); dil=_ep+_em;
 _ep->Rot(dil); _em->Rot(dil); dil->Rot(dil); _ep->Boost(dil); _em->Boost(dil) ;
 s1= _ep->Theta(); _x = cos(s1)


                    Author: I. Froehlich
                    Written: 14.02.2008
                    Revised: