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doc: update Lean.Parser.Basic

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Sebastian Ullrich 2022-11-11 14:17:21 +01:00
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src/Lean/Parser/Basic.lean
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@ -46,8 +46,8 @@ The `Parser` type is extended with additional metadata over the mere parsing fun
token set used to speed up parser selection in `prattParser`. This approach of combining static and dynamic information
in the parser type is inspired by the paper "Deterministic, Error-Correcting Combinator Parsers" by Swierstra and Duponcheel.
If multiple parsers accept the same current token, `prattParser` tries all of them using the backtracking `longestMatchFn` combinator.
This is the only case where standard parsers might execute arbitrary backtracking. At the moment there is no memoization shared by these
parallel parsers apart from the first token, though we might change this in the future if the need arises.
This is the only case where standard parsers might execute arbitrary backtracking. Repeated invocations of the same category or concrete
parser at the same position are cached where possible; see `withCache`.
Finally, error reporting follows the standard combinatoric approach of collecting a single unexpected token/... and zero
or more expected tokens (see `Error` below). Expected tokens are e.g. set by `symbol` and merged by `<|>`. Combinators