When implementing SFINAE using std::enable_if, it is often useful to have access to helper templates that determines if a given type T matches a set of criteria.
To help us with that, the standard already provides two types analog to true and false which are std::true_type and std::false_type.
The...
The begin block is a control structure that groups together multiple statements.
begin
a = 7
b = 6
a * b
end
A begin block will return the value of the last statement in the block. The following example will return 3.
begin
1
2
3
end
The begin block is useful for conditi...
Use 403 Forbidden when a client has requested a resource that is inaccessible due to existing access controls. For example, if your app has an /admin route that should only be accessible to users with administrative rights, you can use 403 when a normal user requests the page.
GET /admin HTTP/1.1
...
s = {1, 2, 3}
# get every element in s
for a in s:
print a # prints 1, then 2, then 3
# copy into list
l1 = list(s) # l1 = [1, 2, 3]
# use list comprehension
l2 = [a * 2 for a in s if a > 2] # l2 = [6]
Use unpacking to extract the first element and ensure it's the only one:
a, = iterable
def foo():
yield 1
a, = foo() # a = 1
nums = [1, 2, 3]
a, = nums # ValueError: too many values to unpack
def gen():
yield 1
iterable = gen()
for a in iterable:
print a
# What was the first item of iterable? No way to get it now.
# Only to get a new iterator
gen()
You can write the default protocol implementation for a specific class.
protocol MyProtocol {
func doSomething()
}
extension MyProtocol where Self: UIViewController {
func doSomething() {
print("UIViewController default protocol implementation")
}
}
class M...
Generic classes can be inherited:
// Models
class MyFirstModel {
}
class MySecondModel: MyFirstModel {
}
// Generic classes
class MyFirstGenericClass<T: MyFirstModel> {
func doSomethingWithModel(model: T) {
// Do something here
}
}
class MySecondGe...
In order to efficiently handle cycle detection, we consider each node as part of a tree. When adding an edge, we check if its two component nodes are part of distinct trees. Initially, each node makes up a one-node tree.
algorithm kruskalMST'(G: a graph)
sort G's edges by their value
MST ...
The above forest methodology is actually a disjoint-set data structure, which involves three main operations:
subalgo makeSet(v: a node):
v.parent = v <- make a new tree rooted at v
subalgo findSet(v: a node):
if v.parent == v:
return v
return findSet(v.parent...
We can do two things to improve the simple and sub-optimal disjoint-set subalgorithms:
Path compression heuristic: findSet does not need to ever handle a tree with height bigger than 2. If it ends up iterating such a tree, it can link the lower nodes directly to the root, optimizing future trav...
Sort the edges by value and add each one to the MST in sorted order, if it doesn't create a cycle.
algorithm kruskalMST(G: a graph)
sort G's edges by their value
MST = an empty graph
for each edge e in G:
if adding e to MST does not create a cycle:
add e to MST
...
You can calculate a number in the Fibonacci sequence using recursion.
Following the math theory of F(n) = F(n-2) + F(n-1), for any i > 0,
// Returns the i'th Fibonacci number
public int fib(int i) {
if(i <= 2) {
// Base case of the recursive function.
// i is either 1...
Each requirements files should match the name of a settings files. Read Using multiple settings for more information.
Structure
djangoproject
├── config
│ ├── __init__.py
│ ├── requirements
│ │ ├── base.txt
│ │ ├── dev.txt
│ │ ├── test.txt
│ │ └── prod.txt
│ └── setti...
var user = Sitecore.Security.Accounts.User.FromName("sitecore/testname", false);
using (new Sitecore.Security.Accounts.UserSwitcher(user))
{
var item = Sitecore.Context.Database.GetItem("/sitecore/content/home");
}
Useful if your program is outputting web pages along the way.
from http.server import HTTPServer, CGIHTTPRequestHandler
import webbrowser
import threading
def start_server(path, port=8000):
'''Start a simple webserver serving path on port'''
os.chdir(path)
httpd = HTTPServer((''...
When you create an argparse ArgumentParser() and run your program with '-h' you get an automated usage message explaining what arguments you can run your software with. By default, positional arguments and conditional arguments are separated into two categories, for example, here is a small script ...
Often times you will see an exception
Anti forgery token is meant for user "" but the current user is "username"
This is because the Anti-Forgery token is also linked to the current logged-in user. This error appears when a user logs in but their token is still linked to bein...
