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What's the safest way to iterate through the keys of a Perl hash?
If I have a Perl hash with a bunch of (key, value) pairs, what is the preferred method of iterating through all the keys? I have heard that using each may in some way have unintended side effects. So, is that true, and is one of the two following methods best, or is there a better way?
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What's the difference between NOT EXISTS vs. NOT IN vs. LEFT JOIN WHERE IS NULL?
...S vs. LEFT JOIN / IS NULL: MySQL
In a nutshell:
NOT IN is a little bit different: it never matches if there is but a single NULL in the list.
In MySQL, NOT EXISTS is a little bit less efficient
In SQL Server, LEFT JOIN / IS NULL is less efficient
In PostgreSQL, NOT IN is less efficient
In Oracl...
Preloading CSS Images
...-index:-1; // hide images
content:url(img1.png) url(img2.png) url(img3.gif) url(img4.jpg); // load images
}
Demo
it's better to use a sprite image to reduce http requests...(if there are many relatively small sized images) and make sure the images are hosted where HTTP2 is used.
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How do I script a “yes” response for installing programs?
... it to) indefinitely. Use it as:
yes | command-that-asks-for-input
or, if a capital 'Y' is required:
yes Y | command-that-asks-for-input
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f...
AngularJS : Difference between the $observe and $watch methods
...$scope changes in AngularJS. But couldn't understand what exactly is the difference between the two.
4 Answers
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rsync error: failed to set times on “/foo/bar”: Operation not permitted
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If /foo/bar is on NFS (or possibly some FUSE filesystem), that might be the problem.
Either way, adding -O / --omit-dir-times to your command line will avoid it trying to set modification times on directories.
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Is there a “do … while” loop in Ruby?
...d he suggests using Kernel#loop, e.g.
loop do
# some code here
break if <condition>
end
Here's an email exchange in 23 Nov 2005 where Matz states:
|> Don't use it please. I'm regretting this feature, and I'd like to
|> remove it in the future if it's possible.
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|I'm surprised...
Why doesn't a python dict.update() return the object?
...ch like the one you appear to wish .update returned -- so why not use THAT if you really feel it's important?
Edit: btw, no need, in your specific case, to create a along the way, either:
dict(name=name, description=desc % count, points=points, parent_award=parent,
**award_dict)
creates a s...
Select every Nth element in CSS
...elements within the same parent element are of the same element type, div. If you have any other elements of different types such as h1 or p, you will need to use :nth-of-type() instead of :nth-child() to ensure you only count div elements:
<body>
<h1></h1>
<div>1</di...
Shallow copy of a Map in Java
...lone method?).
Josh Bloch on Design - Copy Constructor versus Cloning
If you've read the item about cloning in my book, especially if you read between the lines, you will know that I think clone is deeply broken. [...] It's a shame that Cloneable is broken, but it happens.
Bloch (who by the w...