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How to call a parent class function from derived class function?
...disambiguate it by adding the base class's name followed by two colons base_class::foo(...). You should note that unlike Java and C#, C++ does not have a keyword for "the base class" (super or base) since C++ supports multiple inheritance which may lead to ambiguity.
class left {
public:
void f...
How to implement a rule engine?
...;
// use a method call, e.g. 'Contains' -> 'u.Tags.Contains(some_tag)'
return Expression.Call(left, method, right);
}
}
Note that I used 'GreaterThan' instead of 'greater_than' etc. - this is because 'GreaterThan' is the .NET name for the operator, therefore we don't need any...
工作区编排（HarmonyWorkspaceKit）使用指导 · App Inventor 2 中文网
...，将同名事件的处理合并到一个事件积木中。
when 按钮_设备.Click() {
HarmonyWorkspaceKit1.ComposeDeviceControlWorkspace("垂直布局_容器", "compact", "设备控制", "{}", "{}", "#2196F3", "device_")
}
when HarmonyWorkspaceKit1.WorkspaceComposed(种类, 根组件名, 组...
Error to run Android Studio
...l went right the answer should be something like this:
java version "1.8.0_91"
Java(TM) SE Runtime Environment (build 1.8.0_91-b14)
Java HotSpot(TM) 64-Bit Server VM (build 25.91-b14, mixed mode)
Check what compiler is used
javac -version
It should show something like this
javac 1.8.0_91
Fi...
MySQL query String contains
...
Quite simple actually:
mysql_query("
SELECT *
FROM `table`
WHERE `column` LIKE '%{$needle}%'
");
The % is a wildcard for any characters set (none, one or many). Do note that this can get slow on very large datasets so if your database grows you'll nee...
JavaScript and Threads
...rial.
Here is a simple example with 3 Web Worker threads that count to MAX_VALUE and show the current computed value in our page:
//As a worker normally take another JavaScript file to execute we convert the function in an URL: http://stackoverflow.com/a/16799132/2576706
function getScriptPat...
Can a C# lambda expression have more than one statement?
...ven without curly brackets:
Action<int, int> action = (x, y) => (_, _) = (X += x, Y += y);
and
Action<int, int> action = (x, y) => _ = (X += x, Y += y);
would be the same as:
Action<int, int> action = (x, y) => { X += x; Y += y; };
This also might be helpful if yo...
How to use Morgan logger?
...o do logging in the way that servers like Apache and Nginx log to the error_log or access_log. For reference, this is how you use morgan:
var express = require('express'),
app = express(),
morgan = require('morgan'); // Require morgan before use
// You can set morgan to lo...
Simple Log to File example for django 1.3+
...utting this in your settings.py
LOGGING = {
'version': 1,
'disable_existing_loggers': True,
'formatters': {
'standard': {
'format' : "[%(asctime)s] %(levelname)s [%(name)s:%(lineno)s] %(message)s",
'datefmt' : "%d/%b/%Y %H:%M:%S"
},
},
'ha...
Writing a Python list of lists to a csv file
...s pd
In [2]: a = [[1.2,'abc',3],[1.2,'werew',4],[1.4,'qew',2]]
In [3]: my_df = pd.DataFrame(a)
In [4]: my_df.to_csv('my_csv.csv', index=False, header=False)
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