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How to test if list element exists?
...
This is actually a bit trickier than you'd think. Since a list can actually (with some effort) contain NULL elements, it might not be enough to check is.null(foo$a). A more stringent test might be to check that the name is actually defin...
Should I use pt or px?
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px ≠ Pixels
All of these answers seem to be incorrect. Contrary to intuition, in CSS the px is not pixels. At least, not in the simple physical sense.
Read this article from the W3C, EM, PX, PT, CM, IN…, about how px is a "magical" uni...
How to fix Error: listen EADDRINUSE while using nodejs?
... should check for the listening event like this, to see if the server is really listening:
var http=require('http');
var server=http.createServer(function(req,res){
res.end('test');
});
server.on('listening',function(){
console.log('ok, server is running');
});
server.listen(80);
...
MySQL: Can't create table (errno: 150)
... child table InnoDB engine. Current create.sql script was using InnoDB for all tables, but I had very very old installation where first script used MyISAM.
– Whome
Apr 8 '13 at 9:50
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do you have kcachegrind like profiling tools for mac [closed]
...
I ended up using qcachegrind on OSX. It can be installed via brew
brew install qcachegrind
or, to enable graphviz support:
brew install qcachegrind --with-graphviz
What's great about this program is that I successfully loaded a 6.1GB cachegrind file on my MacBook Pro! P...
Java null check why use == instead of .equals()
...l,
// so one of the first checks inside the `Foo#equals` method will
// disallow the equality because it sees that `other` == null
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Normalize data in pandas
... The corresponding method to create unit-normal normalized data is called StandardScaler.
– abeboparebop
Mar 1 '17 at 14:17
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Why doesn't C# support the return of references?
...f (x > y)
return ref x;
else
return ref y;
}
and then call it with
int a = 123;
int b = 456;
ref int c = ref Max(ref a, ref b);
c += 100;
Console.WriteLine(b); // 556!
I know empirically that it is possible to build a version of C# that supports these features because I hav...
Creating a directory in CMake
... make_directory. For example:
add_custom_target(build-time-make-directory ALL
COMMAND ${CMAKE_COMMAND} -E make_directory ${directory})
At install time
To create a directory at install time,
install(DIRECTORY DESTINATION ${directory})
...
Check if element exists in jQuery [duplicate]
... are used therefore "#elementId" selects by element. "elementId" would actually select all emenets whose tags are named "elementId"
– Petr Gladkikh
Dec 13 '12 at 7:13
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