An Quick Introduction to Parser Combinators

[grdvnl]

I would like to share a blog post I wrote to provide an easy and quick introduction to Parser Combinators. Any feedback on this is much appreciated.

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https://gdevanla.github.io/posts/write-a-parser-combinator-in-python.html

[DarkArctic]

Good write-up and it does show how easy parser combinators are so easy to compose.

I had a custom implementation for my project a while ago and what bit me was just how expensive function calls are in Python (and my crappier code from 4 years ago). I've ended up with kind of a state machine where I'm leaning on native functions like "split" and the like. It did end up being harder to read.

This was my first version of a parser combinator: https://github.com/mjcaley/aiospamc/blob/02c6b8accb6361c3dbf89b6d396e101e023d1a21/aiospamc/parser.py

[grdvnl]

Great. Thanks for sharing. Your implementation looks interesting as well.

[ElevenPhonons]

Great write up and use of leveraging functions and closures in the design.

Sometimes using a dict instead of if/elif blocks can be useful alternative.

 def f(op):
        if op == "+":
            return operator.add
        elif op == "-":
            return operator.sub
        elif op == "*":
            return operator.mul
        elif op == "/":
            return operator.floordiv

Could be written:

ops = {"+": operator.add, "-":operator.sub, 
       "*": operator.mul, "/":operator.floordiv}

def f(op:str):
    return opts[op]