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Why can't I forward-declare a class in a namespace using double colons?

... r s t u v w x y z A B C D E F G H I J K L M N O P Q R S T U V W X Y Z _ digit: one of 0 1 2 3 4 5 6 7 8 9 Which is the production of the common scheme [a-zA-Z_][a-zA-Z0-9_]* we are all familiar with. As you can see, this precludes class foo::bar; from being a valid forward declaration, bec...
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Differences between socket.io and websockets

...s) => { console.error('express connection'); res.sendFile(path.join(__dirname, 'ws.html')); }); app.ws('/', (s, req) => { console.error('websocket connection'); for (var t = 0; t < 3; t++) setTimeout(() => s.send('message from server', ()=>{}), 1000*t); }); app.listen(3001...
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Fastest way to determine if an integer's square root is an integer

...04040 computed below { for (int i=0; i<64; ++i) goodMask |= Long.MIN_VALUE >>> (i*i); } public boolean isSquare(long x) { // This tests if the 6 least significant bits are right. // Moving the to be tested bit to the highest position saves us masking. if (goodMask <&l...
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Remove first element from $@ in bash [duplicate]

... Use shift? http://tldp.org/LDP/Bash-Beginners-Guide/html/sect_09_07.html Basically, read $1 for the first argument before the loop (or $0 if what you're wanting to check is the script name), then use shift, then loop over the remaining $@. ...
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xtreme toolkit pro——CXTPReportControl控件教程 - C/C++ - 清泛网 - 专注C/C++及内核技术

...自定义控件,将该控件的class属性改为XTPReport,ID改为;IDC_REPORTCTRL_LIST。 (2)添加一个自定义变量:CXTPReportControl m_wndReportCtrl; (3)将控件和变量联系起来,在对话框初始化函数OnInitDialog()中添加如下代码: m_wndReportCtrlList.Sub...
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Are Swift variables atomic?

..., strong) id engine; @property (atomic, strong) id driver; @end Uses objc_storeStrong and objc_setProperty_atomic for nonatomic and atomic respectively, where class SwiftCar { var engine : AnyObject? init() { } } uses swift_retain from libswift_stdlib_core and, apparently, does ...
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Entity Framework 6 Code first Default value

...unt} nvarchar(128) SELECT @var{dropConstraintCount} = name FROM sys.default_constraints WHERE parent_object_id = object_id(N'{tableSchema}.[{tablePureName}]') AND col_name(parent_object_id, parent_column_id) = '{columnName}'; IF @var{dropConstraintCount} IS NOT NULL EXECUTE('ALTER TABLE {tableSc...
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List comprehension vs map

...oints, but sometimes map seems easier to read to me: data = map(str, some_list_of_objects). Some other ones... operator.attrgetter, operator.itemgetter, etc. – Gregg Lind Aug 8 '09 at 16:06 ...
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how to rotate a bitmap 90 degrees

... source = BitmapFactory.decodeResource(this.getResources(), R.drawable.your_img); share | improve this answer | follow | ...
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How to turn NaN from parseInt into 0 for an empty string?

...h for other stuff, there's a handy defaultTo function that does just this: _.defaultTo(NaN, -1) returns -1, but _.defaultTo(0, -1); returns 0. – waldyrious Dec 6 '18 at 12:40 ...