Class FeynmanDiagramHorizontal

source code

FeynmanDiagram --+
                 |
                FeynmanDiagramHorizontal

Object to compute the position of the different Vertex and Line associate to a diagram object. This routines is quite similar to FeynmanDiagram. The only differences concerns the rules for the y-coordinate of each vertex.

In case of vertex with one and only one S-channel going to the next level. Then force this line to be horizontal. This creates sub-interval where other vertex can be place following the same rule as before (equal distance between vertex) but this time sub-interval by sub-interval.

Finds the vertex position for the particle at 'level' given the 
ordering at previous level given by the vertexlist. 
if auto=True pass in autorecursive mode.

Compare to the function of FeynmanDiagram, this check the number of 
S-channel particles going out of each vertex. If the result is one:
1) Fix the associate vertex at the same y as the original vertex
    -> horizontal line
2) Assign non fix vertex below the fix one in the current interval. 
3) Continue to the next vertex.