Re: Regex to pull out string within parenthesis that could contain parenthesis (updated)

Here's another, more factored example of the use of recursive subpatterns (introduced with Perl version 5.10):

c:\@Work\Perl\monks>perl -wMstrict -MData::Dump -le
"use 5.010;
 ;;
 my $s =
   'function convert(beg string, end string, read_date date, step char
+(6)) returns (date, date, char(1))';
 ;;
 my $rx_paren = qr{ ( [(] (?: [^()]*+ | (?-1))* [)] ) }xms;
 my $rx_identifier = qr{ \w+ }xms;
 ;;
 my $parsed_ok =
 my @ra = $s =~ m{
   \A \s*
   (private|public)? \s*
   (function|report) \s*
   ($rx_identifier)  \s*
   $rx_paren         \s*
   ((returns) \s* $rx_paren)? \s*
   \z
   }xms;
 ;;
 if ($parsed_ok) {
   dd @ra;
   }
 else {
   print 'parse failed';
   }
"
(
  undef,
  "function",
  "convert",
  "(beg string, end string, read_date date, step char(6))",
  "returns (date, date, char(1))",
  "returns",
  "(date, date, char(1))",
)
[download]

Update: The (private|public)? \s* sub-expression in the above m// should probably be something like (untested)
((?: private | public) \s)? \s*
because, e.g., public looks too much like function or report that would always follow it and requires some delimitation.

Give a man a fish: <%-{-{-{-<

Comment on Re: Regex to pull out string within parenthesis that could contain parenthesis (updated) Select or Download Code

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Re^2: Regex to pull out string within parenthesis that could contain parenthesis by TheDamian (Vicar) on Jul 09, 2018 at 21:41 UTC
Here's a variation on the above solution, using named recursive subpatterns and named captures. Nowadays I write all my non-trivial regexes this way. use 5.010; my $source = 'function convert(beg string, end string, read_date date, + step char(6)) returns (date, date, char(1))'; my $matched = $source =~ m{ \A \s+ (?<access> private \| public )?+ \s+ (?<keyword> function \| report ) \s+ (?<name> (?&identifier) ) \s+ (?<params> (?&list) ) \s+ (returns \s+ (?<returns> (?&list) ) )?+ \s+ \z (?(DEFINE) (?<identifier> [^\W\d]\w+ ) (?<list> [(] [^()]+ (?: (?&list) [^()]+ )*+ [)] ) ) }xms; if ($matched) { my %components = %+; use Data::Dumper 'Dumper'; say Dumper \%components; } else { say 'parse failed'; } [download] which outputs: `$VAR1 = { keyword => 'function', name => 'convert', params => '(beg string, end string, read_date date, step char(6))', returns => '(date, date, char(1))', };` [download]	[reply] [d/l] [select]
Re^3: Regex to pull out string within parenthesis that could contain parenthesis by AnomalousMonk (Archbishop) on Jul 09, 2018 at 21:57 UTC
I had entirely forgotten about named captures and `(?(DEFINE)...)` — a much better (regex) approach. Give a man a fish: `<%-{-{-{-<`	[reply] [d/l] [select]


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