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Designing function f(f(n)) == -n
...turn n - 1
else:
return -1 * (n + 1)
Python automatically promotes integers to arbitrary length longs. In other languages the largest positive integer will overflow, so it will work for all integers except that one.
To make it work for real numbers you need to replace the n ...
JavaScript/regex: Remove text between parentheses
...the parentheses are in the middle of a string, the regex above will remove all the whitespace around them. This is probably not good.
– Nigel Johnson
Nov 13 '17 at 11:42
1
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Java Multiple Inheritance
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@MoritzPetersen If you really want to go into reusing abstractions and giving meaningful names, probably AbstractEquidae would be more suitable than AbstractHorse. It would be strange to have a zebra extend an abstract horse. Nice answer, by the way....
Keyboard Interrupts with python's multiprocessing Pool
...s to set up the worker processes to ignore SIGINT altogether, and confine all the cleanup code to the parent process. This fixes the problem for both idle and busy worker processes, and requires no error handling code in your child processes.
import signal
...
def init_worker():
signal.sign...
How to timeout a thread
... SSCCE:
package com.stackoverflow.q2275443;
import java.util.concurrent.Callable;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.Future;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.TimeoutException;
public clas...
How to add Options Menu to Fragment in Android
...
Call the super method:
Java:
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setHasOptionsMenu(true);
}
@Override
public void onCreateOptio...
MongoDB: How to query for records where field is null or not set?
...ount({sent_at: {$exists: false}})
If its there and null, or not there at all:
db.emails.count({sent_at: null})
Refer here for querying and null
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You need to use a Theme.AppCompat theme (or descendant) with this activity
...a subclass, ActionBarActivity), to Activity, must also change the various calls with "support" to the corresponding call without "support". So, instead of getSupportFragmentManager, call getFragmentManager.
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How do I pass an object from one activity to another on Android? [duplicate]
...tom classes across activities. I have found this very useful.
Here is a small snippet of code I am using
CustomListing currentListing = new CustomListing();
Intent i = new Intent();
Bundle b = new Bundle();
b.putParcelable(Constants.CUSTOM_LISTING, currentListing);
i.putExtras(b);
i.setClass(this,...
What does the exclamation mark do before the function?
...s just a function declaration. You would need an invocation, foo(), to actually run the function.
Now, when we add the seemingly innocuous exclamation mark: !function foo() {} it turns it into an expression. It is now a function expression.
The ! alone doesn't invoke the function, of course, but w...