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by tasty_freeze
74 days ago
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Systemverilog has an operator precedence table with 16 levels. https://www.academia.edu/figures/3550818/table-2-operator-pr... Writing a recursive descent for this would require writing 16 functions, and you'd end up spending most of your time cycling through the functions to finally come across the one which applies for the given situation. I've written straight-forward expressions parsers as you suggest, but when I had to do it for systemverilog, I used a classic shunting yard parser. You see the operator, compare its precedence against the stack and you know immediately what to do, vs possibly drilling down 16 levels of function calls to figure out what to do. Another advantage of table-driven expression parsers is you can bail in error cases without needing to unwind countless levels of stack. |
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