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Editorial: two minor tweaks to the RegExp machinery #3503

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Editorial: two minor tweaks to the RegExp machinery #3503

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dc9c8c8
Editorial: replace two stray references to State with MatchState
bakkot Nov 27, 2024
7f30b74
Editorial: replace MatchResult with its definition
bakkot Nov 27, 2024
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13 changes: 5 additions & 8 deletions spec.html
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Original file line number Diff line number Diff line change
Expand Up @@ -36641,16 +36641,13 @@ <h1>Notation</h1>
A <dfn id="pattern-capturerange" variants="CaptureRanges">CaptureRange</dfn> is a Record { [[StartIndex]], [[EndIndex]] } that represents the range of characters included in a capture, where [[StartIndex]] is an integer representing the start index (inclusive) of the range within _Input_, and [[EndIndex]] is an integer representing the end index (exclusive) of the range within _Input_. For any CaptureRange, these indices must satisfy the invariant that [[StartIndex]] ≤ [[EndIndex]].
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<li>
A <dfn id="pattern-matchstate" variants="MatchStates">MatchState</dfn> is a Record { [[Input]], [[EndIndex]], [[Captures]] } where [[Input]] is a List of characters representing the String being matched, [[EndIndex]] is an integer, and [[Captures]] is a List of values, one for each left-capturing parenthesis in the pattern. States are used to represent partial match states in the regular expression matching algorithms. The [[EndIndex]] is one plus the index of the last input character matched so far by the pattern, while [[Captures]] holds the results of capturing parentheses. The _n_<sup>th</sup> element of [[Captures]] is either a CaptureRange representing the range of characters captured by the _n_<sup>th</sup> set of capturing parentheses, or *undefined* if the _n_<sup>th</sup> set of capturing parentheses hasn't been reached yet. Due to backtracking, many States may be in use at any time during the matching process.
A <dfn id="pattern-matchstate" variants="MatchStates" oldids="pattern-matchresult">MatchState</dfn> is a Record { [[Input]], [[EndIndex]], [[Captures]] } where [[Input]] is a List of characters representing the String being matched, [[EndIndex]] is an integer, and [[Captures]] is a List of values, one for each left-capturing parenthesis in the pattern. MatchStates are used to represent partial match states in the regular expression matching algorithms. The [[EndIndex]] is one plus the index of the last input character matched so far by the pattern, while [[Captures]] holds the results of capturing parentheses. The _n_<sup>th</sup> element of [[Captures]] is either a CaptureRange representing the range of characters captured by the _n_<sup>th</sup> set of capturing parentheses, or *undefined* if the _n_<sup>th</sup> set of capturing parentheses hasn't been reached yet. Due to backtracking, many MatchStates may be in use at any time during the matching process.
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<li>
A <dfn id="pattern-matchresult" variants="MatchResults">MatchResult</dfn> is either a MatchState or the special token ~failure~ that indicates that the match failed.
A <dfn id="pattern-matchercontinuation" variants="MatcherContinuations">MatcherContinuation</dfn> is an Abstract Closure that takes one MatchState argument and returns either a MatchState or ~failure~. The MatcherContinuation attempts to match the remaining portion (specified by the closure's captured values) of the pattern against _Input_, starting at the intermediate state given by its MatchState argument. If the match succeeds, the MatcherContinuation returns the final MatchState that it reached; if the match fails, the MatcherContinuation returns ~failure~.
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<li>
A <dfn id="pattern-matchercontinuation" variants="MatcherContinuations">MatcherContinuation</dfn> is an Abstract Closure that takes one MatchState argument and returns a MatchResult result. The MatcherContinuation attempts to match the remaining portion (specified by the closure's captured values) of the pattern against _Input_, starting at the intermediate state given by its MatchState argument. If the match succeeds, the MatcherContinuation returns the final MatchState that it reached; if the match fails, the MatcherContinuation returns ~failure~.
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<li>
A <dfn id="pattern-matcher" variants="Matchers">Matcher</dfn> is an Abstract Closure that takes two arguments—a MatchState and a MatcherContinuation—and returns a MatchResult result. A Matcher attempts to match a middle subpattern (specified by the closure's captured values) of the pattern against the MatchState's [[Input]], starting at the intermediate state given by its MatchState argument. The MatcherContinuation argument should be a closure that matches the rest of the pattern. After matching the subpattern of a pattern to obtain a new MatchState, the Matcher then calls MatcherContinuation on that new MatchState to test if the rest of the pattern can match as well. If it can, the Matcher returns the MatchState returned by MatcherContinuation; if not, the Matcher may try different choices at its choice points, repeatedly calling MatcherContinuation until it either succeeds or all possibilities have been exhausted.
A <dfn id="pattern-matcher" variants="Matchers">Matcher</dfn> is an Abstract Closure that takes two arguments—a MatchState and a MatcherContinuation—and returns either a MatchState or ~failure~. A Matcher attempts to match a middle subpattern (specified by the closure's captured values) of the pattern against the MatchState's [[Input]], starting at the intermediate state given by its MatchState argument. The MatcherContinuation argument should be a closure that matches the rest of the pattern. After matching the subpattern of a pattern to obtain a new MatchState, the Matcher then calls MatcherContinuation on that new MatchState to test if the rest of the pattern can match as well. If it can, the Matcher returns the MatchState returned by MatcherContinuation; if not, the Matcher may try different choices at its choice points, repeatedly calling MatcherContinuation until it either succeeds or all possibilities have been exhausted.
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</ul>

Expand Down Expand Up @@ -36706,7 +36703,7 @@ <h1>RegExp Records</h1>
<h1>
Runtime Semantics: CompilePattern (
_rer_: a RegExp Record,
): an Abstract Closure that takes a List of characters and a non-negative integer and returns a MatchResult
): an Abstract Closure that takes a List of characters and a non-negative integer and returns either a MatchState or ~failure~
</h1>
<dl class="header">
</dl>
Expand Down Expand Up @@ -36811,7 +36808,7 @@ <h1>
_c_: a MatcherContinuation,
_parenIndex_: a non-negative integer,
_parenCount_: a non-negative integer,
): a MatchResult
): either a MatchState or ~failure~
</h1>
<dl class="header">
</dl>
Expand Down