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Should I use string.isEmpty() or “”.equals(string)?
...equals(s) is you don't need the null check (equals will check its argument and return false if it's null), which you seem to not care about. If you're not worried about s being null (or are otherwise checking for it), I would definitely use s.isEmpty(); it shows exactly what you're checking, you ca...
When you exit a C application, is the malloc-ed memory automatically freed?
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It depends on the operating system. The majority of modern (and all major) operating systems will free memory not freed by the program when it ends.
Relying on this is bad practice and it is better to free it explicitly. The issue isn't just that your code looks bad. You may decide y...
Overriding fields or properties in subclasses
I have an abstract base class and I want to declare a field or a property that will have a different value in each class that inherits from this parent class.
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How can I view the source code for a function?
...S4 method dispatch system
The S4 system is a newer method dispatch system and is an alternative to the S3 system. Here is an example of an S4 function:
> library(Matrix)
Loading required package: lattice
> chol2inv
standardGeneric for "chol2inv" defined from package "base"
function (x, ...)...
Does Python have an ordered set?
...s referred to from the Python 2 Documentation. This runs on Py2.6 or later and 3.0 or later without any modifications. The interface is almost exactly the same as a normal set, except that initialisation should be done with a list.
OrderedSet([1, 2, 3])
This is a MutableSet, so the signature for ...
What is __future__ in Python used for and how/when to use it, and how it works
__future__ frequently appears in Python modules. I do not understand what __future__ is for and how/when to use it even after reading the Python's __future__ doc .
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Does Swift have access modifiers?
...e highest (least restrictive) to the lowest (most restrictive).
1. open and public
Enable an entity to be used outside the defining module (target). You typically use open or public access when specifying the public interface to a framework.
However, open access applies only to classes and clas...
What does the Reflect object do in JavaScript?
... http://people.mozilla.org/~jorendorff/es6-draft.html#sec-reflect-object and it sounds similar to the Proxy object apart from the realm and loader functionality.
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MySQL selecting yesterday's date
How can I display and count the values whose dates are yesterday?
I used time() to insert date in the database. Example:
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Convert data.frame column to a vector?
...a frame is a list. When you subset a data frame using the name of a column and [, what you're getting is a sublist (or a sub data frame). If you want the actual atomic column, you could use [[, or somewhat confusingly (to me) you could do aframe[,2] which returns a vector, not a sublist.
So try run...