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Difference between dispatch_async and dispatch_sync on serial queue?
...k is finished whereas dispatch_async return after it is added to the queue and may not finished.
for this code
dispatch_async(_serialQueue, ^{ printf("1"); });
printf("2");
dispatch_async(_serialQueue, ^{ printf("3"); });
printf("4");
It may print 2413 or 2143 or 1234 but 1 always before 3
for ...
WebSockets protocol vs HTTP
There are many blogs and discussions about websocket and HTTP, and many developers and sites strongly advocate websockets, but i still can not understand why.
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Simulator error FBSSystemServiceDomain code 4
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Go to the iOS Simulator menu and select Reset Content and Settings.
Alternatively, you could quit and reopen the Simulator.
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Android studio, gradle and NDK
I am very new to this whole gradle and Android Studio support. I have managed to convert my android project to gradle using the export option.
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Rolling median algorithm in C
...ial window of values, then perform a binary search to insert the new value and remove the existing one at each iteration.
1...
Understanding ibeacon distancing
...estimates.
While the distance estimates are useful, they are not perfect, and require that you control for other variables. Be sure you read up on the complexities and limitations before misusing this.
When we were building the Android iBeacon library, we had to come up with our own independent a...
What is Weak Head Normal Form?
...es Weak Head Normal Form (WHNF) mean? What does Head Normal form (HNF) and Normal Form (NF) mean?
6 Answers
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What is the difference between PS1 and PROMPT_COMMAND
...oc page: http://www.gnu.org/software/bash/manual/bashref.html
PROMPT_COMMAND
If set, the value is interpreted as a command to execute before
the printing of each primary prompt ($PS1).
I never used it, but I could have used this back when I only had sh.
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How to concatenate twice with the C preprocessor and expand a macro as in “arg ## _ ## MACRO”?
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Standard C Preprocessor
$ cat xx.c
#define VARIABLE 3
#define PASTER(x,y) x ## _ ## y
#define EVALUATOR(x,y) PASTER(x,y)
#define NAME(fun) EVALUATOR(fun, VARIABLE)
extern void NAME(mine)(char *x);
$ gcc -E xx.c
# 1 "xx.c"
# ...
Confusion between factor levels and factor labels
There seems to be a difference between levels and labels of a factor in R.
Up to now, I always thought that levels were the 'real' name of factor levels, and labels were the names used for output (such as tables and plots). Obviously, this is not the case, as the following example shows:
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