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How to declare a variable in MySQL?
...DISTINCT IFNULL(@var:=Name,'unknown') FROM Customers ORDER BY <some non-indexed expression> LIMIT 10 appears to evaluate the variable assignments before the order-by is done, so that the returned value of @var might not even relate to any of the returned rows. The docs don't say under what co...
How do I abort the execution of a Python script? [duplicate]
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Prints "aa! errors!" and exits with a status code of 1.
There is also an _exit() function in the os module. The sys.exit() function raises a SystemExit exception to exit the program, so try statements and cleanup code can execute. The os._exit() version doesn't do this. It just ends the program...
How to Apply Gradient to background view of iOS Swift App
...ems you may face with this is that when you add a sublayer it may sit over all your other items, labels, image, etc. To overcome this create another view that sits below everything and set its constraints to that of the container you want the gradient in. Then set the gradient to be applied to this ...
Why do x86-64 systems have only a 48 bit virtual address space?
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Because that's all that's needed. 48 bits give you an address space of 256 terabyte. That's a lot. You're not going to see a system which needs more than that any time soon.
So CPU manufacturers took a shortcut. They use an instruction set...
Restore file from old commit in git
...efault) puts it in working tree. If you want to put the change directly in index so it can be committed straight away:
git restore --source=abcdef --worktree --staged file_name
or with short option names:
git restore -s=abcdef -W -S file_name
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How are virtual functions and vtable implemented?
...e, it's indeed structure-like. But in other contexts, but the idea of vtbl index is useful (e.g. ActiveX uses it in the way it describes dual interfaces in typelibs), which is a more array-like view.
– puetzk
Aug 2 '18 at 14:12
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[完整源码实例] 修改 CListCtrl 的标题栏字体颜色；重绘 CListCtrl 标题栏 ...
... 0, // cStrikeOut
ANSI_CHARSET, // nCharSet
OUT_DEFAULT_PRECIS, // nOutPrecision
CLIP_DEFAULT_PRECIS, // nClipPrecision
DEFAULT_QUALI...
How to detect total available/free disk space on the iPhone/iPad device?
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Original answer:
I found the following solution working for me:
-(uint64_t)getFreeDiskspace {
uint64_t totalSpace = 0;
uint64_t totalFreeSpace = 0;
NSError *error = nil;
NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
NSDic...
How to see which flags -march=native will activate?
I'm compiling my C++ app using GCC 4.3. Instead of manually selecting the optimization flags I'm using -march=native , which in theory should add all optimization flags applicable to the hardware I'm compiling on. But how can I check which flags is it actually using?
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What are the “standard unambiguous date” formats for string-to-date conversion in R?
...te (+1). However, the error message "standard unambiguous format" is ironically ambiguous, to which the 23 previous questions attest. A more direct error message like, "format not recognized, see documentation" might improve user experience. Also, I don't believe "01/01/2000" is ISO-8601 ("2000-01-0...