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Re: Let's talk about trim() so more

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From:
Tony Cook
Date:
March 31, 2021 23:40
Subject:
Re: Let's talk about trim() so more
Message ID:
20210331234019.GO13843@venus.tony.develop-help.com
On Wed, Mar 31, 2021 at 11:19:22AM -0400, Dan Book wrote:
> Just a slight addendum to this and Ben's excellent detail of the situation:
> the "effectively in-place" form can be (and I believe may already be, in
> the PR) optimized as a built-in to an actual in-place operation even when
> you don't write it as one.

Simple cases could be, like:

  my $x;
  $x = trim($x);

More complex variants:

  my @x;
  my $i;
  ...
  $x[$i] = trim $x[$i]; # $i might be magical

can't really be optimized that way.

The existing PR does optimize on:

  $y = trim $x;

where $y and $x, however complex they are as expressions, turn out to
be the same SV, but the code doesn't try to eliminate any other
duplication. eg. if $x and $y are lexicals, two padsv ops are produced.

Tony
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