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Backwards migration with Django South
... one you want to roll back.
Your app should have a migrations directory, with files in it named like
0000_initial.py
0001_added_some_fields.py
0002_added_some_more_fields.py
0003_deleted_some_stuff.py
Normally, when you run ./manage.py migrate your_app, South runs all new migrations, in order. (...
Using awk to remove the Byte-order mark
...==1{sub(/^\xef\xbb\xbf/,"")}1' INFILE > OUTFILE
1 is the shortest condition that always evaluates to true, so each record is printed.
Enjoy!
-- ADDENDUM --
Unicode Byte Order Mark (BOM) FAQ includes the following table listing the exact BOM bytes for each encoding:
Bytes | Encoding...
The smallest difference between 2 Angles
...360 - 180
Beware in many languages the modulo operation returns a value with the same sign as the dividend (like C, C++, C#, JavaScript, full list here). This requires a custom mod function like so:
mod = (a, n) -> a - floor(a/n) * n
Or so:
mod = (a, n) -> (a % n + n) % n
If angles are...
Cast List to List
...
You can't cast it (preserving reference identity) - that would be unsafe. For example:
public interface IFruit {}
public class Apple : IFruit {}
public class Banana : IFruit {}
...
List<Apple> apples = new List<Apple>();
Lis...
Set Focus on EditText
I have an EditText-Field and set an OnFocusChangeListener for it. When it has lost focus, a method is called, which checks the value of the EditText with one in the database. If the return-value of the method is true, a toast is shown and the focus should get back on the EditText again. The focus sh...
What is ActiveMQ used for - can we apply messaging concept using a Database?
I looked it up and it used to send messages between 2 systems.
But why? Why wouldn't you just use a Database ?
There must be some feature that ActiveMQ has that Databases do not?
...
How to apply multiple styles in WPF
...dy has a style. I also have a separate style which I would like to add to it without blowing away the first one. The styles have different TargetTypes, so I can't just extend one with the other.
...
Method Resolution Order (MRO) in new-style classes?
In the book Python in a Nutshell (2nd Edition) there is an example which uses
old style classes to demonstrate how methods are resolved in classic resolution order and
how is it different with the new order.
...
Do C# Timers elapse on a separate thread?
...stem.Timers.Timer elapse on a separate thread than the thread that created it?
5 Answers
...
Is returning by rvalue reference more efficient?
...urn move(Beta_ab(1, 1));
}
This returns a dangling reference, just like with the lvalue reference case. After the function returns, the temporary object will get destructed. You should return Beta_ab by value, like the following
Beta_ab
Beta::toAB() const {
return Beta_ab(1, 1);
}
Now, i...