in reply to Re^5: Using pos() inside regexp (no /e)
in thread Using pos() inside regexp

There isn't two functions with the same name. (That doesn't even make sense.) It's not read-only.

s/// uses the specified position when it starts matching (not in the middle), and only for \G. As mentioned by someone else, it makes no sense to modify the pos s/// uses in the middle of its operation.

If you want to move pos back, you would want to the input with one thing, then replace it again with something else. Replace it with the right thing the first time.

If you want to move pos forward, s/// has no way to know what you want to do with the chunk you're skipping over. Should it be copied? Should it be replaced?

Replies are listed 'Best First'.
Re^7: Using pos() inside regexp (no /e)
by andal (Hermit) on Oct 13, 2010 at 08:58 UTC
    I understand your arguments. But the point is simple. Using "pos() = $new_pos" does not work during the matching process. So either the "perldoc -f pos" has to be updated, or the function available during matching should be renamed. Of course, more appropriate is to update the description of "pos" function. This way we wouldn't need to argue about what makes sense and what does not. Everything would be nice and clear. The update of the last match position is possible only outside of matching. This is exactly what I meant in my first message.
[reply]

      Using "pos() = $new_pos" does not work during the matching process.

      That is also wrong. pos works in a substitution expression just like it does outside a substitution expression. Had you checked, you would have seen that lvalue pos does in fact change the var's pos when used in the substitution expression. 

      $ perl -E'my $x="abc"; $x=~s/./say pos($x); pos($x)=2; say pos($x)/e;'
0
2

      [download]

      s/// simply doesn't care that you changed it. Like I've already explained, it simply doesn't make any sense for s/// to check if the string's pos has changed. Why are you still asking about this?

[reply]
[d/l]
[select]
        What's the difference? The change does not have any effect on the matching. So it is the same as not working at all. After your matching ends, the set value won't even be preserved. So, for the original question "Can pos() be used inside of matching to change where the \G matches" the answer is "No. The pos does not work during matching. In other words, it does not affect the position where the \G matches". And this should be written in the documentation.
[reply]

In Section Seekers of Perl Wisdom