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micro:bit 微控制器教程 · App Inventor 2 中文网
...用 WriteRXCharacteristic 指令来发送 “R\n” 这样的字符串，R 是根据不同按钮的控制指令，\n 是换行符号，代表一个命令的结尾。
用 anyButton.TouchUp 来管理所有按钮的 touchUp 事件，缺点是 Disconnect 按钮也算进去，您可以在事件中加...
Fastest way to iterate over all the chars in a String
...e strings as byte[] by default.
SECOND UPDATE: As of 2016-10-25, on my AMDx64 8core and source 1.8, there is no difference between using 'charAt' and field access. It appears that the jvm is sufficiently optimized to inline and streamline any 'string.charAt(n)' calls.
THIRD UPDATE: As of 2020-09-07,...
How to find out what type of a Mat object is with Mat::type() in OpenCV
...e CV_32S: r = "32S"; break;
case CV_32F: r = "32F"; break;
case CV_64F: r = "64F"; break;
default: r = "User"; break;
}
r += "C";
r += (chans+'0');
return r;
}
If M is a var of type Mat you can call it like so:
string ty = type2str( M.type() );
printf("Matrix: %s %dx%d ...
libunwind链接时报错：undefined reference to `_Ux86_64_init_local\' - ...
libunwind链接时报错：undefined reference to `_Ux86_64_init_local'编译安装libunwind后，代码编译链接时报错：undefined reference to `_Ux86_64_init_local& 39;，链接选项加了 -lunwind，仍然报错。原因：编译出来的libunwind拆分成了很多个 编译安装libunwi...
Web API Put Request generates an Http 405 Method Not Allowed error
...PI-4.0_32bit" />
<remove name="ExtensionlessUrlHandler-ISAPI-4.0_64bit" />
<remove name="ExtensionlessUrlHandler-Integrated-4.0" />
<add name="ExtensionlessUrlHandler-ISAPI-4.0_32bit" path="*." verb="GET,HEAD,POST,DEBUG,PUT,DELETE,PATCH,OPTIONS" modules="IsapiModule" sc...
Different floating point result with optimization enabled - compiler bug?
...ssors use 80-bit extended precision internally, whereas double is normally 64-bit wide. Different optimization levels affect how often floating point values from CPU get saved into memory and thus rounded from 80-bit precision to 64-bit precision.
Use the -ffloat-store gcc option to get the same fl...
Rounding up to next power of 2
... that time?). From : jameshfisher.com/2018/03/30/round-up-power-2.html uint64_t next_pow2(uint64_t x) { return x == 1 ? 1 : 1<<(64-__builtin_clzl(x-1)); } And for 32 bit : uint32_t next_pow2(uint32_t x) { return x == 1 ? 1 : 1<<(32-__builtin_clz(x-1)); } That is if you use GCC (and Cla...
Download a file by jQuery.Ajax
...
You can with HTML5
NB: The file data returned MUST be base64 encoded because you cannot JSON encode binary data
In my AJAX response I have a data structure that looks like this:
{
result: 'OK',
download: {
mimetype: string(mimetype in the form 'major/minor'),
...
SQL Server Configuration Manager not found
...an directly browse it using this paths..
SQL Server 2019 C:\Windows\SysWOW64\SQLServerManager15.msc
SQL Server 2017 C:\Windows\SysWOW64\SQLServerManager14.msc
SQL Server 2016 C:\Windows\SysWOW64\SQLServerManager13.msc
SQL Server 2014 C:\Windows\SysWOW64\SQLServerManager12.msc
SQL Server 2012 ...
How to get current timestamp in milliseconds since 1970 just the way Java gets
...e <chrono>
#include <iostream>
int main() {
unsigned __int64 now = std::chrono::duration_cast<std::chrono::milliseconds>(std::chrono::system_clock::now().time_since_epoch()).count();
std::cout << now << std::endl;
return 0;
}
...