RegExp: Syntax for referencing named backreference from within a replacement string?

[lth]

Cf msg by Steven Levithan on es4-discuss: both Python and Perl/.NET provide named submatches, and provide ways of referencing the names from replace strings. In ES3 we have $n and $nn within the replace string to extract and use submatches, it's likely an oversight that we don't have similar functionality for named submatches.

According to Steven, Python uses \g<name> and Perl/.NET use \k<name>, where I assume the angle brackets are literal. Neither makes much sense for ES4, since ES3 uniformly uses $ as the character signalling replacement text substitution. Considering the use of (?P<name>...) for matching, $<name> would not be bad.

[lth]

See #266 for a related issue.

[lth]

I meant #256, of course.

[StevenLevithan]

Thanks for opening these tickets, lth. Note that Python's \g<name> and Perl/.NET's \k<name> are not equivalent. One is used for backreferences in a replacement string, while the other is used for a backreference in the regex. I've summarized the differences between named capture syntax in all current languages which support the feature under the heading "Named capture" at http://stevenlevithan.com/regex/xregexp/ (which is the documentation page for a forthcoming JavaScript? library I'm working on).

While I agree that $<name> would not be bad, personally I would recommend .NET's ${name}, since that already follows the prior art of some other regex libraries which use ${n} to remove ambiguity between backreferences, octals, and literal numbers.

[airforce1]

thanks get a nice air force ones