Suggest adopting .NET/Perl regexp named capture syntax

[StevenLevithan]

ECMAScript 4 regular expression extension proposals indicate that the Python
syntax will be used for named capture. Python uses (?P<name>...) for named
capture, (?P=name) for a backreference within the regex, and \g<name> for a
backreference within a replacement string. Personally, I feel this a
mistake.

Although Python was the first to implement named capture, other libraries
seem to be standardizing around .NET's alternative syntax, which uses
(?<name>...) or (?'name'...) for capture, \k<name> or \k'name' for a
backreference within the regex, and ${name} for a backreference within a
replacement string. Perl 5.10 has adopted .NET's syntax (although
backrefereces within a replacement string use $+{name}) since "most people
consider it to be nicer". Recent versions of PCRE have followed Perl's lead
by supporting .NET's syntax for named capture as the preferred style.

Here are the problems I see with the Python syntax:

(?P<name>...)
- What does the "P" stand for? "Python"? The character is unnecessary and
unhelpful.

(?P=name)
- Backreferences should not use parentheses since they are a single token
and not a grouping.

\g<name>
- Is this a single token in ES4, or a string which in a string literal will
have to be written as "\\g<name>"? If it is the former, how will you be able
to generate a replacement string using e.g. a textarea with user input, and
if it's the latter, it seems less elegant than ${name} , which follows the
'$ denotes a backreference' convention.

One other question... can the results from named capture be used in a
replacement closure function? I.e., will you be able to do something like
str.replace(/(?P<name>)/,function(match){return match.name;}); ?
-- 
View this message in context: http://www.nabble.com/Suggest-adopting-.NET-Perl-regexp-named-capture-syntax-tf4682705.html#a13380696
Sent from the Mozilla - ECMAScript 4 discussion mailing list archive at Nabble.com.