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How do I perform the SQL Join equivalent in MongoDB?
...ttps://docs.mongodb.org/master/reference/operator/aggregation/lookup/#pipe._S_lookup
From the docs:
{
$lookup:
{
from: <collection to join>,
localField: <field from the input documents>,
foreignField: <field from the documents of the "from" collection>...
How can I add reflection to a C++ application?
...re are some handy macros to help with typed expressions:
#define REM(...) __VA_ARGS__
#define EAT(...)
// Retrieve the type
#define TYPEOF(x) DETAIL_TYPEOF(DETAIL_TYPEOF_PROBE x,)
#define DETAIL_TYPEOF(...) DETAIL_TYPEOF_HEAD(__VA_ARGS__)
#define DETAIL_TYPEOF_HEAD(x, ...) REM x
#define DETAIL_TYP...
Bash continuation lines
...here document. (Line terminators will still remain, though.)
cat <<-____HERE
continuation
lines
____HERE
See also http://ss64.com/bash/syntax-here.html
If you need to preserve some, but not all, leading whitespace, you might use something like
sed 's/^ //' <<____HERE
Th...
Syntax Error: Not a Chance
...indentation will never be implemented.
Normally, imports from the special __future__ module enable features that are backwards-incompatible, such as the print() function, or true division.
So the line from __future__ import braces is taken to mean you want to enable the 'create blocks with braces'...
How to list imported modules?
...ems():
if isinstance(val, types.ModuleType):
yield val.__name__
This won't return local imports, or non-module imports like from x import y. Note that this returns val.__name__ so you get the original module name if you used import module as alias; yield name instead if you wa...
How do I import other TypeScript files?
...ler as follows:
tsc --module amd app.ts
This then gets compiled to
var __extends = this.__extends || function (d, b) {
function __() { this.constructor = d; }
__.prototype = b.prototype;
d.prototype = new __();
}
define(["require", "exports", 'moo'], function(require, exports, __moo_...
Can I create links with 'target=“_blank”' in Markdown?
...d, you'll just have to use HTML.
<a href="http://example.com/" target="_blank">Hello, world!</a>
Most Markdown engines I've seen allow plain old HTML, just for situations like this where a generic text markup system just won't cut it. (The StackOverflow engine, for example.) They then...
Passing parameters in rails redirect_to
How do we pass parameters in redirect_to in rails?
I know we can pass id using this:
9 Answers
...
What is the difference between a field and a property?
...It is private to your class and stores the actual data.
private string _myField;
// this is a property. When accessed it uses the underlying field,
// but only exposes the contract, which will not be affected by the underlying field
public string MyProperty
{
get
...
How do I print the elements of a C++ vector in GDB?
...td::vector<int> called myVector, do the following:
print *(myVector._M_impl._M_start)@myVector.size()
To print only the first N elements, do:
print *(myVector._M_impl._M_start)@N
Explanation
This is probably heavily dependent on your compiler version, but for GCC 4.1.2, the pointer to t...