in reply to Re: Reversed .= operator
in thread Reversed .= operator

Yes, of course, there is more than one way to do it. I would use 

$string = $prefix . $string

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over 
substr $string, 0, 0, $prefix

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myself (for readability, not because it's two fewer characters) ... but I want a (built-in) operator, dammit!


The way forward always starts with a minimal test.

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Re^3: Reversed .= operator
by choroba (Cardinal) on Apr 29, 2016 at 22:25 UTC
    It's not the same. substr is a bit faster, probably because it doesn't create a new string?

    ($q=q:Sq=~/;[c](.)(.)/;chr(-||-|5+lengthSq)`"S|oS2"`map{chr |+ord
}map{substrSq`S_+|`|}3E|-|`7**2-3:)=~y+S|`+$1,++print+eval$q,q,a,

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      Is $string =~ s/^/$prefix/; about the same speed as the substr expression?

      To me, it would more signal the intent than substr does. Then again, so does the pesky dot-between-strings notation, which 1nickt doesn't want. :-) But, as with the substr, the =~ s/^// version doesn't require duplicating $string in your statement, which is one of the benefits of the suffixing .= operator.

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        Here's the benchmark code:
        Read more... (1071 Bytes)

        Here's the result on my machine: 

        ok 1 - correct concat
ok 2 - same substr
ok 3 - same subst
1..3
            Rate  subst precat substr
subst  1770916/s     --   -38%   -47%
precat 2860656/s    62%     --   -15%
substr 3350927/s    89%    17%     --

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        ($q=q:Sq=~/;[c](.)(.)/;chr(-||-|5+lengthSq)`"S|oS2"`map{chr |+ord
}map{substrSq`S_+|`|}3E|-|`7**2-3:)=~y+S|`+$1,++print+eval$q,q,a,

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