Re: Does s/\Q$find\E/$replace/g really a plain string replace ?

Sometimes, it's just easier to try it out:

$_       = 'foo bah bar';
$find    = 'bah';
$replace = '[\1]';
s/(\Q$find\E)/$replace/g;

$\ = "\n";
print;      # "foo [\1] bar" and not "foo [bah] bar"
[download]

But there is indeed a (more efficient?) way:

$_       = 'foo bah bar';
$find    = 'bah';
$replace = '[\1]';

$idx = index($_, $find);
substr($_, $idx, length($find), $replace) if $idx >= 0;

$\ = "\n";
print;
[download]

Update: Here's a version that does mutliple matches:

$_       = 'foo bah bah bar';
$find    = 'bah';
$replace = '[\1]';

$idx = length($_);
while (($idx = rindex($_, $find, $idx-1)) >= 0) {
   substr($_, $idx, length($find), $replace);
}

$\ = "\n";
print;
[download]

Comment on Re: Does s/\Q$find\E/$replace/g really a plain string replace ? Select or Download Code

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Re^2: Does s/\Q$find\E/$replace/g really a plain string replace ? by diotalevi (Canon) on Oct 02, 2004 at 16:23 UTC
Good job. You forgot to accomodate the /g on the regexp. I'd prefer to write this as a s///g but here's your version, reconstituted for the /g feature. `while ( ( my $index = index substr( $_, pos() ), $find), $index != -1 ) { substr $_, $index, length $find, $replace; pos() = $index + length $find; }` [download] `while ( ( my $index = index $_, $find), $index != -1 ) { substr $_, $index, length $find, $replace; }` [download]	[reply] [d/l] [select]
Re^3: Does s/\Q$find\E/$replace/g really a plain string replace ? by ikegami (Patriarch) on Oct 02, 2004 at 16:32 UTC
At the same time you were writting that, I was writting my own /g! Mine doesn't have an infinite loop like yours does, however. Try yours with: `$_ = 'foo bah bar'; $find = 'bah'; $replace = '[bah]'; first time in loop: foo [bah] bar second time in loop: foo [[bah]] bar third time in loop: foo [[[bah]]] bar ...` [download]	[reply] [d/l]
Re^2: Does s/\Q$find\E/$replace/g really a plain string replace ? by !1 (Hermit) on Oct 02, 2004 at 21:57 UTC
`$_ = 'foo bbbbbbbah bar'; $find = 'bah'; $replace = 'ah';` [download] and `$_ = 'foo babab bar'; $find = 'bab'; $replace = 'xxx';` [download] don't work very well. Perhaps something like: `sub replace { die "Some helpful messsage" unless 3 == grep defined $_, @_[0..2]; my ($str,$find,$rep) = @_; my $i = 0; my $l = length($find); my @pos; while ($i < length($str)) { $i = index($str,$find,$i); last if $i < 0; push @pos, $i; $i += $l; } substr($str,$_,$l,$rep) for reverse @pos; return $str; }` [download]	[reply] [d/l] [select]