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How do you set, clear, and toggle a single bit?
... behaviour to shift by more than the width of a long. The same applies to all the rest of the examples.
Clearing a bit
Use the bitwise AND operator (&) to clear a bit.
number &= ~(1UL << n);
That will clear the nth bit of number. You must invert the bit string with the bitwise NOT op...
Find difference between timestamps in seconds in PostgreSQL
...
Try:
SELECT EXTRACT(EPOCH FROM (timestamp_B - timestamp_A))
FROM TableA
Details here: EXTRACT.
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How to avoid “Permission denied” when using pip with virtualenv
...ed Oct 19 '13 at 23:02
sebastian_oesebastian_oe
6,63822 gold badges1515 silver badges2020 bronze badges
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Setting UIButton image results in blue button in iOS 7
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In iOS7 there is new button type called UIButtonTypeSystem NS_ENUM_AVAILABLE_IOS(7_0), // standard system button
Check your .xib file and change button type to Custom
To do this programmatically, add this line to the viewDidLoad:
[UIButton buttonWithType...
Mix Razor and Javascript code
...avascript blocks when executed but I hate how the syntax highlighting gets all sorts of confused. It highlights all the Razor code as invalid Syntax because it's stuck in Javascript mode I believe.
– Chev
Aug 10 '12 at 16:29
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How can I pretty-print JSON using Go?
...NewFormatter()
f.Indent = 4
// Marshall the Colorized JSON
s, _ := f.Marshal(obj)
fmt.Println(string(s))
}
I'm writing the documentation for it now but I was excited to share my solution.
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How can I determine if a variable is 'undefined' or 'null'?
...enceError and break execution if variable is not defined or referred to at all in the code, using typeof is safer.
– Mani Gandham
Jun 15 '14 at 9:49
59
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How to check if there exists a process with a given pid in Python?
... if the pid is not running, and do nothing otherwise.
import os
def check_pid(pid):
""" Check For the existence of a unix pid. """
try:
os.kill(pid, 0)
except OSError:
return False
else:
return True
...
Bash array with spaces in elements
...through its indices, like so, it works if I add the elements either numerically or with escapes:
for ((i = 0; i < ${#FILES[@]}; i++))
do
echo "${FILES[$i]}"
done
Any of these declarations of $FILES should work:
FILES=(2011-09-04\ 21.43.02.jpg
2011-09-05\ 10.23.14.jpg
2011-09-09\ 12.31.16....
leading zeros in rails
...using a given padding character.
str.rjust(integer, padstr=' ') → new_str
If integer is greater than the length of str, returns a new String of length integer with str right justified and padded with padstr; otherwise, returns str.
some_int = 5
some_int.to_s.rjust(2, '0') # => '05'
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