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How do I call one constructor from another in Java?
...
Yes, it is possible:
public class Foo {
private int x;
public Foo() {
this(1);
}
public Foo(int x) {
this.x = x;
}
}
To chain to a particular superclass constructor instead of one in the same class, use super instead of this. Note that you c...
Nested defaultdict of defaultdict
...ber of levels:
def rec_dd():
return defaultdict(rec_dd)
>>> x = rec_dd()
>>> x['a']['b']['c']['d']
defaultdict(<function rec_dd at 0x7f0dcef81500>, {})
>>> print json.dumps(x)
{"a": {"b": {"c": {"d": {}}}}}
Of course you could also do this with a lambda, but ...
Where and why do I have to put the “template” and “typename” keywords?
...why do I have to put typename and template on dependent names?
What exactly are dependent names anyway?
6 Answers
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What are good uses for Python3's “Function Annotations”
...no constructs that made this straightforward and part of the official syntax.
There are other uses for annotations beyond assurance. I can see how I could apply my Java-based tools to Python. For instance, I have a tool that lets you assign special warnings to methods, and gives you indications wh...
C# 4.0 optional out/ref arguments
...ication, section 21.1:
Formal parameters of constructors, methods, indexers and delegate types can be declared optional:
fixed-parameter:
attributesopt parameter-modifieropt type identifier default-argumentopt
default-argument:
= expression
A fixed-parameter ...
iPhone UIButton - image position
I have a UIButton with text "Explore the app" and UIImage (>)
In Interface Builder it looks like:
15 Answers
...
Drawing an image from a data URL to a canvas
...ge or purely in JS) by setting the src of the image to your data URL. For example:
var img = new Image;
img.src = strDataURI;
The drawImage() method of HTML5 Canvas Context lets you copy all or a portion of an image (or canvas, or video) onto a canvas.
You might use it like so:
var myCanvas = d...
How do I extract a sub-hash from a hash?
...
If you specifically want the method to return the extracted elements but h1 to remain the same:
h1 = {:a => :A, :b => :B, :c => :C, :d => :D}
h2 = h1.select {|key, value| [:b, :d, :e, :f].include?(key) } # => {:b=>:B, :d=>:D}
h1 = Hash[h1.to_a - h2.to_a...
How to get first element in a list of tuples?
...st(unzipped[0])
[1, 2]
Edit (@BradSolomon):
The above works for Python 2.x, where zip returns a list.
In Python 3.x, zip returns an iterator and the following is equivalent to the above:
>>> print(list(list(zip(*inpt))[0]))
[1, 2]
...
Determining memory usage of objects? [duplicate]
...time ago I stole this little nugget from here:
sort( sapply(ls(),function(x){object.size(get(x))}))
it has served me well
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