What kind of formal languages can modern regex engines parse?

Question

Here on SO people sometimes say something like \"you cannot parse X with regular expressions, because X is not a regular language\". From my understanding however, modern re

Answer 1

You can read about regexes in An Introduction to Language And Linguistics By Ralph W. Fasold, Jeff Connor-Linton P.477

Chomsky Hierarchy:

Type0 >= Type1 >= Type2 >= Type3

Computational Linguistics mainly features Type 2 & 3 Grammars

• Type 3 grammars:

–Include regular expressions and finite state automata (aka, finite state machines)

–The focal point of the rest of this talk

• Type 2 grammars:

–Commonly used for natural language parsers

–Used to model syntactic structure in many linguistic theories (often supplemented by other mechanisms)

–We will play a key roll in the next talk on parsing.

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most XMLs like Microsoft DGML (Directed Graph Markup Language) that has inter-relational links are samples that Regex are useless.

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and this three answers may be useful:

1 - does-lookaround-affect-which-languages-can-be-matched-by-regular-expressions

2 - regular-expressions-arent

3 - where-do-most-regex-implementations-fall-on-the-complexity-scale