class TF12: public TF1

 TF12 default constructor

 TF12 normal constructor.
   Create a TF12 (special TF1) from a projection of a TF2
   for a fix value of Y if option="X" or X if option="Y"
 This value may be changed at any time via TF12::SetXY(xy)

 F2 default destructor.

 Copy constructor.

 Copy this F2 to a new F2.

 Draw a copy of this function with its current attributes.

  This function MUST be used instead of Draw when you want to draw
  the same function with different parameters settings in the same canvas.

 Possible option values are:
   "SAME"  superimpose on top of existing picture
   "L"     connect all computed points with a straight line
   "C"     connect all computed points with a smooth curve.

 Note that the default value is "F". Therefore to draw on top
 of an existing picture, specify option "SL"

 Evaluate this formula

   Computes the value of the referenced TF2 for a fix value of X or Y

 Evaluate this function at point x[0]
   x[0] is the value along X if fCase =0, the value along Y if fCase=1
 if params is non null, the array will be used instead of the internal TF2
 parameters

 Save primitive as a C++ statement(s) on output stream out

 set the value of the constant for the TF2
   constant in X when projecting along Y
   constant in Y when projecting along X
  The function title is set to include the value of the constant
  The current pad is updated