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What is the copy-and-swap idiom?
...s arguably the most nuanced and difficult. How should it be done? What pitfalls need to be avoided?
The copy-and-swap idiom is the solution, and elegantly assists the assignment operator in achieving two things: avoiding code duplication, and providing a strong exception guarantee.
How does it wor...
How do you get the list of targets in a makefile?
...ed rake a bit (a Ruby make program), and it has an option to get a list of all the available targets, eg
20 Answers
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How to JSON serialize sets?
...s.
As shown in the json module docs, this conversion can be done automatically by a JSONEncoder and JSONDecoder, but then you would be giving up some other structure you might need (if you convert sets to a list, then you lose the ability to recover regular lists; if you convert sets to a dictionar...
Why dict.get(key) instead of dict[key]?
...
It allows you to provide a default value if the key is missing:
dictionary.get("bogus", default_value)
returns default_value (whatever you choose it to be), whereas
dictionary["bogus"]
would raise a KeyError.
If omitted...
ModelSerializer using model property
... Meta is optional. If you omit fields, in the above example, you would get all the MyModel fields plus ext_link in the serialized data. And this is really awesome for complex models! EDIT: At least, this is true for djangorestframework==2.3.14.
– e.thompsy
Feb ...
jQuery - replace all instances of a character in a string [duplicate]
...round the string, as replace is not a jQuery method, so that won't work at all.)
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decorators in the python standard lib (@deprecated specifically)
...r('always', DeprecationWarning) # turn off filter
warnings.warn("Call to deprecated function {}.".format(func.__name__),
category=DeprecationWarning,
stacklevel=2)
warnings.simplefilter('default', DeprecationWarning) # reset filter
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What exactly does git's “rebase --preserve-merges” do (and why?)
...it, and deal with some extra wrinkles
The most interesting part, conceptually, is perhaps in picking what the new commit's merge parents should be.
Replaying merge commits also require explicitly checking out particular commits (git checkout <desired first parent>), whereas normal rebase do...
Why does viewWillAppear not get called when an app comes back from the background?
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In other words, if someone looks at another application or takes a phone call, then switches back to your app which was earlier on backgrounded, your UIViewController which was already visible when you left your app 'doesn't care' so to speak -- as far as it is concerned, it's never disappeared and...
Apache Spark: map vs mapPartitions?
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I'm seeing the opposite -- even with very small operations, its faster to call mapPartitions and iterate than call map. I am assuming that this is just the overhead of starting the language engine that will process the map task. (I'm in R, which may have more startup...