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Re: What is the purpose of '||=' in the example code for Spreadsheet::XLSX

by tobyink (Abbot)
on Nov 14, 2012 at 20:05 UTC ( #1003887=note: print w/replies, xml ) Need Help??

in reply to What is the purpose of '||=' in the example code for Spreadsheet::XLSX

"My guess is that if MaxRow or MaxCol are undefined then they are set to equal MinRow or MinCol respectfully."

Very close. But it's not if they're undefined. It's if they're false. Undefined things are false, but so is 0, and so is the empty string, and so can be objects which overload boolification.

The //= operator would do what you originally suggested. It specifically checks undefinedness, not falseness.

The //= operator was introduced in Perl 5.10, so people wanting to do defined-or-assign while supporting ancient versions of Perl are forced to choose between ||= (which might not be quite what they want - maybe they need to differentiate between undef and 0) or a more longwinded:

$sheet->{MaxRow} = $sheet->{MinRow} unless defined $sheet->{MaxRow};
perl -E'sub Monkey::do{say$_,for@_,do{($monkey=[caller(0)]->[3])=~s{::}{ }and$monkey}}"Monkey say"->Monkey::do'

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[Discipulus]: ah! so you mean if i need a static image i can use Twig, if on the fly better css selector and mody attrs (jquery?), rigth?
[LanX]: not sure what you guys are taking about, but a DOM manipulation in JS shouldn't be difficult
[Corion]: Discipulus: Yeah, that's what I would try (but so far, I can't even change the colors manually in the SVG, which is why I gave up ;) )
Discipulus bad sign..
[Discipulus]: italian doc says to modify somehow the initial SVG before using it with D3.js
[Discipulus]: LanX the fact is that my js ability is even poorer than my Perl one..
[LanX]: oh its negative? ;P

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