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What are “first class” objects?
...as
any other object.
A first class object is an entity that can be dynamically created, destroyed, passed to a function, returned as a value, and have all the rights as other variables in the programming language have.
Depending on the language, this can
imply:
being expressible as ...
How to implement a rule engine?
...Rules = rules.Select(r => CompileRule(r)).ToList();
public bool MatchesAllRules(User user)
{
return compiledRules.All(rule => rule(user));
}
Here is the implementation of BuildExpr:
Expression BuildExpr(Rule r, ParameterExpression param)
{
var left = MemberExpression.Property(param, ...
std::enable_if to conditionally compile a member function
... I want to use std::enable_if to choose between two member-functions and allow only one of them to be used.
7 Answers
...
How do you get a list of the names of all files present in a directory in Node.js?
I'm trying to get a list of the names of all the files present in a directory using Node.js. I want output that is an array of filenames. How can I do this?
...
namedtuple and default values for optional keyword arguments
...lds)
>>> Node()
Node(val=None, left=None, right=None)
Order
In all versions of Python, if you set fewer default values than exist in the namedtuple, the defaults are applied to the rightmost parameters. This allows you to keep some arguments as required arguments.
>>> Node.__ne...
Compare object instances for equality by their attributes
...s:
>>> x == y
True
Note that implementing __eq__ will automatically make instances of your class unhashable, which means they can't be stored in sets and dicts. If you're not modelling an immutable type (i.e. if the attributes foo and bar may change value within the lifetime of your obje...
How to write a scalable Tcp/Ip based server
...he best bet, using the Asynchronous sockets. This meant that clients not really doing anything actually required relatively little resources. Anything that does occur is handled by the .net thread pool.
I wrote it as a class that manages all connections for the servers.
I simply used a list to ho...
What does “mro()” do?
...very attribute you get on a class's instance, not just methods, is conceptually looked up along the __mro__, so, if more than one class among the ancestors defines that name, this tells you where the attribute will be found -- in the first class in the __mro__ that defines that name.
...
How do I get my Python program to sleep for 50 milliseconds?
...rity, CPU load avg, available memory, and a plethora of other factors make all calls imprecise. The busier the system is, the higher the imprecision.
– David
Jan 28 '19 at 18:44
2...
Multiple variables in a 'with' statement?
...textlib.nested, this guarantees that a and b will have their __exit__()'s called even if C() or it's __enter__() method raises an exception.
You can also use earlier variables in later definitions (h/t Ahmad below):
with A() as a, B(a) as b, C(a, b) as c:
doSomething(a, c)
...