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authorNobuyoshi Nakada <nobu@ruby-lang.org>2021-02-11 22:20:41 +0900
committerNobuyoshi Nakada <nobu@ruby-lang.org>2021-02-11 22:20:41 +0900
commitf3f78f96548e10e76784b2b45771b41dd358afd2 (patch)
tree076b56f99936cf2db335423987c0969decfa9877 /doc
parent8544f51ef70b6b34aa6c81f5b52a4f05da464609 (diff)
[DOC] Improved regexp.rdoc [ci skip]
* Sub-sectioned "Repetition" section * Added examples of "Possessive match"
Diffstat (limited to 'doc')
-rw-r--r--doc/regexp.rdoc10
1 files changed, 10 insertions, 0 deletions
diff --git a/doc/regexp.rdoc b/doc/regexp.rdoc
index d84cae1..e25f10f 100644
--- a/doc/regexp.rdoc
+++ b/doc/regexp.rdoc
@@ -190,6 +190,8 @@ At least one uppercase character ('H'), at least one lowercase character
"Hello".match(/[[:upper:]]+[[:lower:]]+l{2}o/) #=> #<MatchData "Hello">
+=== Greedy match
+
Repetition is <i>greedy</i> by default: as many occurrences as possible
are matched while still allowing the overall match to succeed. By
contrast, <i>lazy</i> matching makes the minimal amount of matches
@@ -206,11 +208,17 @@ Both patterns below match the string. The first uses a greedy quantifier so
/<.+>/.match("<a><b>") #=> #<MatchData "<a><b>">
/<.+?>/.match("<a><b>") #=> #<MatchData "<a>">
+=== Possessive match
+
A quantifier followed by <tt>+</tt> matches <i>possessively</i>: once it
has matched it does not backtrack. They behave like greedy quantifiers,
but having matched they refuse to "give up" their match even if this
jeopardises the overall match.
+ /<.*><.+>/.match("<a><b>") #=> #<MatchData "<a><b>">
+ /<.*+><.+>/.match("<a><b>") #=> nil
+ /<.*><.++>/.match("<a><b>") #=> nil
+
== Capturing
Parentheses can be used for <i>capturing</i>. The text enclosed by the
@@ -230,6 +238,8 @@ available with its #[] method:
/[csh](..) [csh]\1 in/.match("The cat sat in the hat")[1] #=> 'at'
+=== Named captures
+
Capture groups can be referred to by name when defined with the
<tt>(?<</tt><i>name</i><tt>>)</tt> or <tt>(?'</tt><i>name</i><tt>')</tt>
constructs.