Sync with master.

diff --git a/src/manual/submatch/submatch.rst_ b/src/manual/submatch/submatch.rst_
index eebf0ec1acb810a9989153080782a1a43753a26b..8d1bfd658c742bd770d2a57e2ac7c81c7b1bd825 100644 (file)
--- a/src/manual/submatch/submatch.rst_
+++ b/src/manual/submatch/submatch.rst_
@@ -1,9 +1,17 @@
-Re2c has two options for submatch extraction.
+Submatch extraction in re2c is based on the lookahead-TDFA algorithm described
+in the
+`Tagged Deterministic Finite Automata with Lookahead <https://arxiv.org/abs/1907.08837>`_
+paper. The algorithm uses the notion of "tags" --- position markers that denote
+positions in the regular expression for which the lexer must determine the
+corresponding position in the input string.
+Re2c provides two options for submatch extraction: the first one allows to use
+raw tags, and the second one allows to use the more conventional parenthesized
+capturing groups.
 
 The first option is ``-T --tags``. With this option one can use standalone tags
 of the form ``@stag`` and ``#mtag``, where ``stag`` and ``mtag`` are arbitrary
-used-defined names. Tags can be used anywhere inside of a regular expression;
-semantically they are just position markers. Tags of the form ``@stag`` are
+used-defined names. Tags can be used anywhere inside of a regular expression.
+Tags of the form ``@stag`` are
 called s-tags: they denote a single submatch value (the last input position
 where this tag matched). Tags of the form ``#mtag`` are called m-tags: they
 denote multiple submatch values (the whole history of repetitions of this tag).
@@ -24,12 +32,9 @@ maximal value of ``yynmatch`` among all rules. Note that re2c implements
 POSIX-compliant disambiguation: each subexpression matches as long as possible,
 and subexpressions that start earlier in regular expression have priority over
 those starting later. Capturing groups are translated into s-tags under the
-hood, therefore we use the word "tag" to describe them as well.
+hood.
 
-With both ``-P --posix-captures`` and ``T --tags`` options re2c uses efficient
-submatch extraction algorithm described in the
-`Tagged Deterministic Finite Automata with Lookahead <https://arxiv.org/abs/1907.08837>`_
-paper. The overhead on submatch extraction in the generated lexer grows with the
+The overhead on submatch extraction in the generated lexer grows with the
 number of tags --- if this number is moderate, the overhead is barely
 noticeable. In the lexer tags are implemented using a number of tag variables
 generated by re2c. There is no one-to-one correspondence between tag variables