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Create PostgreSQL ROLE (user) if it doesn't exist
.... The DO statement uses plpgsql as default procedural language. The syntax allows to omit the explicit declaration:
DO [ LANGUAGE lang_name ] code
...
lang_name
The name of the procedural language the code is written in. If
omitted, the default is plpgsql.
...
Modifying location.hash without page scrolling
...reated and placed at the current location of the scroll. It's the same visually as position:fixed/top:0. Thus the scrollbar is "moved" to the exact same spot it currently is on.
– Borgar
Sep 29 '09 at 0:44
...
C++ catching all exceptions
...
try{
// ...
} catch (...) {
// ...
}
will catch all C++ exceptions, but it should be considered bad design. You can use c++11's new current_exception mechanism, but if you don't have the ability to use c++11 (legacy code systems requiring a rewrite), then you have no name...
Why doesn't GCC optimize a*a*a*a*a*a to (a*a*a)*(a*a*a)?
...scientific application. One thing I noticed is that GCC will optimize the call pow(a,2) by compiling it into a*a , but the call pow(a,6) is not optimized and will actually call the library function pow , which greatly slows down the performance. (In contrast, Intel C++ Compiler , executable ...
App Inventor 2 向心力实验App - 探究向心力F与角速度ω、半径r、质量m的关...
...a
初始化局部变量 m = 取文本为数字(文本输入框_质量.文本)
初始化局部变量 r = 取文本为数字(文本输入框_半径.文本)
设置 全局变量 向心力 为 m × 全局变量 向心加速度
设置 标...
Linux chmod命令用法 - 更多技术 - 清泛网 - 专注C/C++及内核技术
Linux chmod命令用法chmod----改变一个或多个文件的存取模式(mode)chmod [options] mode files只能文件属主或特权用户才能使用该功能来改变文件存取模式。mo...chmod----改变一个或多个文件的存取模式(mode)
chmod [options] mode files
只能文...
pdf预览功能研究形成文档：[url]https://puravidaapps.com/snippets.php#2p...
pdf预览功能研究形成文档：https://puravidaapps.com/snippets.php#2pdfpdf完成，但这个文档里面还有很多东西，需要整理。
Refused to display in a frame because it set 'X-Frame-Options' to 'SAMEORIGIN'
...ight='760' src="https://www.youtube.com/embed/dQw4w9WgXcQ" frameborder="0" allowfullscreen></iframe>
– backwardm
Aug 5 '15 at 20:28
2
...
低功耗蓝牙内置版使用指导 · App Inventor 2 中文网
...。
案例一：按名称连接设备
when 按钮_连接.Click() {
BluetoothLowEnergy1.ConnectMatchingName(文本输入框_设备名称.Text)
}
when BluetoothLowEnergy1.Connected() {
标签1.Text = "已连接"
}
when BluetoothLowEnergy1.ConnectionFailed(原因) {
标...
Transposing a 2D-array in JavaScript
...
array[0].map((_, colIndex) => array.map(row => row[colIndex]));
map calls a provided callback function once for each element in an array, in order, and constructs a new array from the results. callback is invoked only for indexe...