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Difference between “git checkout ” and “git checkout -- ”
...ould normally discard uncommitted changes
# to the _file_ "README"
git checkout master # would normally switch the working copy to
# the _branch_ "master"
git checkout -- master # discard uncommitted changes to the _file_ "master"
and option/f...
Programmatically find the number of cores on a machine
...<thread>
//may return 0 when not able to detect
const auto processor_count = std::thread::hardware_concurrency();
Reference: std::thread::hardware_concurrency
In C++ prior to C++11, there's no portable way. Instead, you'll need to use one or more of the following methods (guarded by app...
Preloading images with JavaScript
...OP:
var preloadImage = function (url) {
try {
var _img = new Image();
_img.src = url;
} catch (e) { }
}
Standard:
function preloadImage (url) {
try {
var _img = new Image();
_img.src = url;
} catch (e) { ...
What is a regular expression for a MAC Address?
...perty \p{xdigit} includes the FULLWIDTH versions. You might prefer \p{ASCII_Hex_Digit} instead.
The answer to the question asked might be best answered — provided you have a certain venerable CPAN module installed — by typing:
% perl -MRegexp::Common -lE 'say $RE{net}{MAC}'
I show the partic...
What is Func, how and when is it used
...PrintListToConsole<T> {
private PrintListConsoleRender<T> _renderer;
public void SetRenderer(PrintListConsoleRender<T> r) {
// this is the point where I can personalize the render mechanism
_renderer = r;
}
public void PrintToConsole(List<T>...
What characters are valid for JavaScript variable names?
...mmarizing the relevant spec sections:
An identifier must start with $, _, or any character in the Unicode categories “Uppercase letter (Lu)”, “Lowercase letter (Ll)”, “Titlecase letter (Lt)”, “Modifier letter (Lm)”, “Other letter (Lo)”, or “Letter number (Nl)”.
The r...
Code Golf - π day
...
Perl, 95 96 99 106 109 110 119 characters:
$t+=$;=1|2*sqrt($r**2-($u-2*$_)**2),say$"x($r-$;/2).'*'x$;for 0..
($u=($r=<>)-1|1);say$t*2/$r**2
(The newline can be removed and is only there to avoid a scrollbar)
Yay! Circle version!
$t+=$;=
1|2*sqrt($r**
2-($u-2*$_)**2)
,say$"x($r-$;/2
)....
What's the difference between lists and tuples?
...e pairs of page and line number to reference locations in a book, e.g.:
my_location = (42, 11) # page number, line number
You can then use this as a key in a dictionary to store notes on locations. A list on the other hand could be used to store multiple locations. Naturally one might want to ad...
Iterate over the lines of a string
...< 0: break
yield foo[prevnl + 1:nextnl]
prevnl = nextnl
if __name__ == '__main__':
for f in f1, f2, f3:
print list(f())
Running this as the main script confirms the three functions are equivalent. With timeit (and a * 100 for foo to get substantial strings for more precise me...
Convert pem key to ssh-rsa format
...pub -i -mPKCS8
From the ssh-keygen docs (From man ssh-keygen):
-m key_format Specify a key format for the -i (import) or -e (export) conversion options. The supported key formats are: “RFC4716” (RFC 4716/SSH2 public or private key), “PKCS8” (PEM PKCS8 public key) or “PEM” (PEM pub...