Re: while loop -> map

On 5/25/05, Jeff 'japhy' Pinyan <japhy@xxxxxxxxxxxx> wrote:
> On May 25, Jay Savage said:
>
> > /e(?{push @bar, pos})/g;
> >
> > should work, but seems to ignore the /g.
>
> Because as you wrote it, the regex is in void context, which means it'll
> only match once. Put it in list context:
>
> () = /e(?{ push @bar, pos })/g;
>
> But this looks weird to almost anyone. I'd do:
>
> /e(?{ push @bar, pos })(?!)/;

Thanks. this makes sense. But why does the zero-width lookahead
force list context? And why does /g by itself force list context for
s/// with the same search string?

>
> If 'e' is more than one character, you'll need to use
>
> /(?>pattern)(?{ push @bar, pos })(?!)/;

Assuming that the patter to matc on = "pattern", this works, too:

/p(?:{push @bar, pos})attern(?!)/g

>
> You could also use $-[0] instead of pos().
>

That depends on the context. $-[0] holds the value of the beginning of
the current match. pos() returns the position at the end of the
current match, i.e. $+[0], and is what the OP used. $-[0] = pos() -
length($&), more or less. For single-character matches, this has the
effect of making values returned from $-[0] zero indexed, and values
returned from pos() one indexed. (That's also why any (?{}) expression
with pos needs to be inserted after the frist character of a
multi-character match.)

--jay
--------------------
daggerquill [at] gmail [dot] com
http://www.engatiki.org
.

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