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> I frankly think we're still waiting for a 'gold standard' in regular expression implementation. Is it the implementations, or is it regexes themselves? I was

by e12e 5y ago

> I frankly think we're still waiting for a 'gold standard' in regular expression implementation. Is it the implementations, or is it regexes themselves? I was under the impression that SNOBOL/SPITBOL/REBOL was the gold standard... But I guess you're saying that given some (posix?) regex syntax, implementations can/should be improved? (while eg REBOL/Red-lang goes more towards "a more pragmatic regular language for pattern recognition", I guess ?)

9214 5y ago
> REBOL/Red-lang goes more towards "a more pragmatic regular language for pattern recognition" Rebol and Red use embedded PEG parsers, which, by definition, support context-free, and not just regular, languages.
- glangdale 5y ago
  I'm fascinated by PEG parsers, but I don't know whether they can be implemented in a way that's remotely as performant as even mediocre regular expression implementations, much less tuned SIMD extravaganzas. That would be a stretch goal for me: build a regular expression / automata library that's sufficiently modular to keep some components and drop in more expressive constructs (not necessarily PEGs, but maybe pushdown automata).
  - e12e 5y ago
    Not, sure - but I just came across this in the Nim standard library: http://nim-lang.github.io/Nim/pegs.html http://nim-lang.github.io/Nim/pegs.html > Simple PEG (Parsing expression grammar) matching. Uses no memorization, but uses superoperators and symbol inlining to improve performance. Note: Matching performance is hopefully competitive with optimized regular expression engines.
    - glangdale 5y ago
      I've written a lot of things that are "hopefully competitive" with something else, but generally benchmarking is the ideal. :-) Hard to benchmark PEG vs regex fairly. Not dismissing it out of hand, as I've had many years to observe the weak spots of regex at quite a short distance.

by e12e 5y ago

9214 5y ago

> REBOL/Red-lang goes more towards "a more pragmatic regular language for pattern recognition" Rebol and Red use embedded PEG parsers, which, by definition, support context-free, and not just regular, languages.

glangdale 5y ago
I'm fascinated by PEG parsers, but I don't know whether they can be implemented in a way that's remotely as performant as even mediocre regular expression implementations, much less tuned SIMD extravaganzas. That would be a stretch goal for me: build a regular expression / automata library that's sufficiently modular to keep some components and drop in more expressive constructs (not necessarily PEGs, but maybe pushdown automata).
- e12e 5y ago
  Not, sure - but I just came across this in the Nim standard library: http://nim-lang.github.io/Nim/pegs.html http://nim-lang.github.io/Nim/pegs.html > Simple PEG (Parsing expression grammar) matching. Uses no memorization, but uses superoperators and symbol inlining to improve performance. Note: Matching performance is hopefully competitive with optimized regular expression engines.
  - glangdale 5y ago
    I've written a lot of things that are "hopefully competitive" with something else, but generally benchmarking is the ideal. :-) Hard to benchmark PEG vs regex fairly. Not dismissing it out of hand, as I've had many years to observe the weak spots of regex at quite a short distance.