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What does “coalgebra” mean in the context of programming?
....)
This lets us talk about algebras as a type τ with a single function from some mess of Eithers to a single τ. For monoids, this mess is: Either (τ, τ) (); for groups (which have an extra τ → τ operation), it's: Either (Either (τ, τ) τ) (). It's a different type for every different stru...
C++ templates that accept only certain types
...
I suggest using Boost's static assert feature in concert with is_base_of from the Boost Type Traits library:
template<typename T>
class ObservableList {
BOOST_STATIC_ASSERT((is_base_of<List, T>::value)); //Yes, the double parentheses are needed, otherwise the comma will be seen as...
Trim last character from a string
...rim method.
Trim - Removes all occurrences of
white space characters from the
beginning and end of this instance.
MSDN-Trim
Under this definition removing only last character from string is bad solution.
So if we want to "Trim last character from string" we should do something like thi...
What is a “slug” in Django?
...-virgin
In this example, the-46-year-old-virgin is a slug: it is created from the title by down-casing all letters, and replacing spaces by hyphens -.
Also see the URL of this very web page for another example.
share
...
Why is “import *” bad?
...it puts a lot of stuff into your namespace (might shadow some other object from previous import and you won't know about it).
Because you don't know exactly what is imported and can't easily find from which module a certain thing was imported (readability).
Because you can't use cool tools like py...
Trying to mock datetime.date.today(), but not working
....com/spulec/freezegun/
Install it:
pip install freezegun
And use it:
from freezegun import freeze_time
@freeze_time("2012-01-01")
def test_something():
from datetime import datetime
print(datetime.now()) # 2012-01-01 00:00:00
from datetime import date
print(date.today()) # ...
How can I make XSLT work in chrome?
...197, issue 111905).
Imagine this scenario:
You receive an email message from an attacker containing a web page as an attachment, which you download.
You open the now-local web page in your browser.
The local web page creates an <iframe> whose source is https://mail.google.com/mail/.
Because...
Why have header files and .cpp files? [closed]
...
Well, the main reason would be for separating the interface from the implementation. The header declares "what" a class (or whatever is being implemented) will do, while the cpp file defines "how" it will perform those features.
This reduces dependencies so that code that uses the h...
How can I convert an RGB image into grayscale in Python?
...
How about doing it with Pillow:
from PIL import Image
img = Image.open('image.png').convert('LA')
img.save('greyscale.png')
Using matplotlib and the formula
Y' = 0.2989 R + 0.5870 G + 0.1140 B
you could do:
import numpy as np
import matplotlib.pypl...
Generate Java class from JSON?
In a Java Maven project, how do you generate java source files from JSON? For example we have
13 Answers
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