Re: substr() - copying or not copying, that is here the question.

In article <87h60zrbea.fsf@bsb.me.uk>, Ben Bacarisse  <ben@bsb.me.uk> wrote:
...

An alternative (depending on the context) would be to consider an
extension that provides an index function with a third argument giving
the initial offset.  I've not looked at how extensions get access to
GAWK strings, so this many not be as easy as it sounds, but I would
guess that it might be relatively simple to do.

The thing about writing GAWK extensions is that the first one is hard,
because it is all new stuff to learn (and you have to establish your own
conventions for how your extensions are going to look, code-wise).  But once
you've written one, the second is much easier and it gets progressively
easier after that.  You want to get to a point where to write a new
extension, you just take the previous one you wrote, copy it to a new name,
do a global search/replace of "oldname" with "newname", delete the
operative code from the old extension, replace it with the new operative
code (which is usually a very small amount of actual code) - and, you're done.

I think that an index()-like function that starts the search at a given
offset into the main string (say, position 900000 of a one million
character string) would be both a good idea and pretty easy to implement as
an extension.  I could do it - at least modulo i18n.  My version would be
C locale only.  Note that index() doesn't do regexps; the search would be
straight string only - using strstr() (or strcasestr() if IGNORECASE is
set).

By the way, if you find the substring at position 900005 (i.e., the 5th (*)
char of the searched string), should the function return 5 or 900005?

(*) Or 6th; I'm not sure of my exact notation at this point.

--
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