From: Robert Klemme <shortcutter@...>
Date: 2009-12-15T00:20:25+09:00
Subject: Re: Ruby 1.9 string slicing and StringScanner pointers

2009/12/14 Brian Candler <b.candler@pobox.com>:
> Caio Chassot wrote:
>> Should this be considered a bug in StringScanner? Wouldn't it make more
>> sense for it to use character indexes?

It would seem so.

> I suspect the reason it does it this way is because it's very expensive
> in ruby 1.9 to jump to the Nth character. So if you were scanning a
> large string, it would get slower and slower as you scanned further
> along, calling #scan each time.

I don't know StringScanner internals, but does this have to be so?  I
mean, with $' you get the remainder of the string so when not using
positions you could handle it that way at the expense of an additional
String instance for each match.

> I think what you're doing is the only option: tag the string as a
> single-byte encoding ("ASCII-8BIT" would be better than "US-ASCII"),
> select the range of bytes, and tag it back again, relying on the fact
> that strscan has chomped a whole number of characters.

Or use String#scan or another matching option, if that is possible.

Kind regards

robert

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