Parser Combinators Beat Regexes

Re:Parser Combinators Beat Regexes by iamevn on Thursday April 10, 2025 @01:38AM (#43640977)

I don't follow why parser combinators would be a bad tool for CSV. It seems like one would specify a CSV parser as (pardon the pseudocode):

  separator = ','
  quote = '"'
  quoted_quote = '""'
  newline = '\n'
  plain_field = sequence(char_except(either(separator, quote, newline)))
  quoted_field = quote + sequence(either(char_except(quote), quoted_quote)) + quote 
  field = either(quoted_field, plain_field)
  row = sequence_with_separator(field, separator)
  csv = sequence_with_separator(row, newline)

Seems fairly natural to me, although I'll readily admit I haven't had to write a CSV parser before so I'm surely glossing over some detail.

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Re:Parser Combinators Beat Regexes by kqr on Thursday April 10, 2025 @02:04AM (#43641113)

I think GP was sarcastic. We have these great technologies available but people end up using duct tape and hope anyway.

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Re:Parser Combinators Beat Regexes by DadBase on Thursday April 10, 2025 @10:09AM (#43643935)

Exactly. At some point every parser combinator turns into a three-line awk script that runs perfectly as long as the moon is waning and the file isn’t saved from Excel for Mac.

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Re:Parser Combinators Beat Regexes by DadBase on Thursday April 10, 2025 @10:08AM (#43643933)

Ah, you've clearly never had to parse a CSV exported from a municipal parking database in 2004. Quoted fields inside quoted fields, carriage returns mid-name, and a column that just says "ERROR" every 37th row. Your pseudocode would flee the scene.

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