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What is a higher kinded type in Scala?
...e used classes were defined as:
class String
class List[T]
class Functor[F[_]]
To avoid the indirection through defining classes, you need to somehow express anonymous type functions, which are not expressible directly in Scala, but you can use structural types without too much syntactic overhead (...
How to search a specific value in all tables (PostgreSQL)?
...
How about dumping the contents of the database, then using grep?
$ pg_dump --data-only --inserts -U postgres your-db-name > a.tmp
$ grep United a.tmp
INSERT INTO countries VALUES ('US', 'United States');
INSERT INTO countries VALUES ('GB', 'United Kingdom');
The same utility, pg_dump, can...
Creating a blocking Queue in .NET?
...ublic class BlockingQueue<T>
{
private readonly Subject<T> _queue;
private readonly IEnumerator<T> _enumerator;
private readonly object _sync = new object();
public BlockingQueue()
{
_queue = new Subject<T>();
_enumerator = _queue.GetEnume...
MongoDB副本集详解 优于以往的主从模式 - 大数据 & AI - 清泛网 - 专注C/C++及内核技术
...ngodb.org/downloads
实验环境使用的Mongodb版本为mongodb-linux-x86_64-2.6.0
由三台虚拟机搭建，配置为单核,1G内存。实验环境如下:
MongoDB的副本集不同于以往的主从模式。
在集群Master故障的时候，副本集可以自动投票，选举出新的Maste...
LINQ to Entities case sensitive comparison
...ase sensitivity is at the mercy of your SQL Server which by default has SQL_Latin1_General_CP1_CI_AS Collation and that is NOT case sensitive.
Using ObjectQuery.ToTraceString to see the generated SQL query that has been actually submitted to SQL Server reveals the mystery:
string sqlQuery = ((Object...
Check if a Windows service exists and delete in PowerShell
...ee Remove-Service doc)
For example:
$service = Get-WmiObject -Class Win32_Service -Filter "Name='servicename'"
$service.delete()
Or with the sc.exe tool:
sc.exe delete ServiceName
Finally, if you do have access to PowerShell 6.0:
Remove-Service -Name ServiceName
...
How can I manually generate a .pyc file from a .py file
...ividual files(s) from the command line with:
python -m compileall <file_1>.py <file_n>.py
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Simplest way to detect a mobile device in PHP
...
Detect Mobile Browser
Download PHP script
Code:
<?php
$useragent=$_SERVER['HTTP_USER_AGENT'];
if(preg_match('/(android|bb\d+|meego).+mobile|avantgo|bada\/|blackberry|blazer|compal|elaine|fennec|hiptop|iemobile|ip(hone|od)|iris|kindle|lge |maemo|midp|mmp|netfront|opera m(ob|in)i|palm( os)?|...
How to run a python script from IDLE interactive shell?
...s.call(['python', 'helloworld.py']) # Just run the program
subprocess.check_output(['python', 'helloworld.py']) # Also gets you the stdout
With arguments:
subprocess.call(['python', 'helloworld.py', 'arg'])
Read the docs for details :-)
Tested with this basic helloworld.py:
import sys
if le...
How can I check if a Perl array contains a particular value?
...
Simply turn the array into a hash:
my %params = map { $_ => 1 } @badparams;
if(exists($params{$someparam})) { ... }
You can also add more (unique) params to the list:
$params{$newparam} = 1;
And later get a list of (unique) params back:
@badparams = keys %params;
...