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What is the purpose of the reader monad?
... is it equipped with? What is it good for?
How is the monad implemented? From where does it arise?
From the first approach, the reader monad is some abstract type
data Reader env a
such that
-- Reader is a monad
instance Monad (Reader env)
-- and we have a function to get its environment
as...
What's the difference between deadlock and livelock?
...
Taken from http://en.wikipedia.org/wiki/Deadlock:
In concurrent computing, a deadlock is a state in which each member of a group of actions, is waiting for some other member to release a lock
A livelock is similar to a deadlock,
e...
Add Variables to Tuple
..., 2, 3, 4, 5, 6)
c = b[1:] # (2, 3, 4, 5, 6)
And, of course, build them from existing values:
name = "Joe"
age = 40
location = "New York"
joe = (name, age, location)
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How to print a number with commas as thousands separators in JavaScript
...
I used the idea from Kerry's answer, but simplified it since I was just looking for something simple for my specific purpose. Here is what I did:
function numberWithCommas(x) {
return x.toString().replace(/\B(?=(\d{3})+(?!\d))/g, ",");
...
How do you delete an ActiveRecord object?
... 'value') will allow you to delete records
without a primary key
Note: from @hammady's comment, user.destroy won't work if User model has no primary key.
Note 2: From @pavel-chuchuva's comment, destroy_all with conditions and delete_all with conditions has been deprecated in Rails 5.1 - see gui...
How does the C code that prints from 1 to 1000 without loops or conditional statements work?
I've found C code that prints from 1 to 1000 without loops or conditionals :
But I don't understand how it works. Can anyone go through the code and explain each line?
...
Java string to date conversion
...though when the format pattern seems valid.
Here's an extract of relevance from the javadoc, listing all available format patterns:
Letter Date or Time Component Presentation Examples
------ ---------------------- ------------------ -------------------------------------
G Era desig...
Are parallel calls to send/recv on the same socket valid?
...e talking about POSIX send/recv then yes, you can call them simultaneously from multiple threads and things will work.
This doesn't necessarily mean that they'll be executed in parallel -- in the case of multiple sends, the second will likely block until the first completes. You probably won't not...
throw new std::exception vs throw std::exception
... (probably logging related code)
}
Note that yourexception should derive from std::exception directly or indirectly.
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How to find out how many lines of code there are in an Xcode project?
...and it is fairly easy to use. It is a PERL script that you can add and run from your project directory.
PERL is already part of Mac OS and you can invoke the script this way to find out your number of lines you have written:
perl cloc-1.56.pl ./YourDirectoryWhereYourSourcesAre
This is an example...