How to handle nodes with identical names at different levels of the tree?

[martonmiklos]

I am trying to make a parser for a GenCAD file to be used in the InteractiveHtmlBom. I made grammar from the GenCAD specs for a different project written in C and parsed with mpc. I tailored the grammar for parsimonious and parsing works fine, but I am struggling how to extract data properly.

GenCAD represents a PCB design which means it has a lot of graphical primitive (line, arc, circle, etc) which appears in many different objects.

Like the line appears in multiple places, and in first place I would need the board's lines only:

board               = "$BOARD" n+ thickness? (line/arc/circle/rectangle/cutout/mask/artwork/attribute/text)* n* "$ENDBOARD" n*`
...
artwork             = "ARTWORK" s name s layer n (line/arc/circle/rectangle/type/filled)*

If I write a visitor for the board I see the lines/arcs in the children, but I cannot distinguish them.

If I write a visitor for visit_line it will give all lines regardless their parents..

I tried 'aliasing':

board_line      = line
board               = "$BOARD" n+ thickness? (board_line/arc/circle/rectangle/cutout/mask/artwork/attribute/text)* n* "$ENDBOARD" n*

but the visit_board_line never get called. And on the another hand aliasing would extend the already long (170 lines) of grammar.

Is there a golden approach overcoming this problem?

[liancheng]

IIUC, the problem is that you cannot distinguish the context where line appears. The context is mostly decided by the parent rule invoking line. Therefore, one possible way is to return a Line object from visit_line, and annotate it further in your visit_board and visit_artwork visitor methods (e.g., setting something like a LineType field in the Line object`).

[martonmiklos]

IIUC, the problem is that you cannot distinguish the context where line appears. The context is mostly decided by the parent rule invoking line. Therefore, one possible way is to return a Line object from visit_line, and annotate it further in your visit_board and visit_artwork visitor methods (e.g., setting something like a LineType field in the Line object`).

Hi, many thanks for the reply. In the meantime I sorted it out, I could access the names in the following way: https://github.com/martonmiklos/InteractiveHtmlBom/blob/gencad/InteractiveHtmlBom/ecad/gencad.py#L71