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std::function and std::bind: what are they, and when should they be used?
...nd to get g:
auto g = bind(f, _1, 4, _2);
This is more concise than actually writing a functor class to do it.
There are further examples in the article you link to. You generally use it when you need to pass a functor to some algorithm. You have a function or functor that almost does the job yo...
Passing a 2D array to a C++ function
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@Zack: You're right, there're only really two cases; one is a pointer-to-pointer and other being a single pointer to an integer array of size n i.e. int (*a) [10].
– legends2k
Jul 10 '13 at 10:44
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How to save all the variables in the current python session?
I want to save all the variables in my current python environment. It seems one option is to use the 'pickle' module. However, I don't want to do this for 2 reasons:
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Dynamic cell width of UICollectionView depending on label width
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You cannot imagine how I thank you! That really works. Now I only need to resolve [cell.myLabel sizeToFit] problem, because it appears in its full size only after scrolling. But I have not been even close to your solution.
– pulp
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convert UIImage to NSData
...ata* data = (id)CFBridgingRelease(CGDataProviderCopyData(provider));
const uint8_t* bytes = [data bytes];
This will give you the low-level representation of the image RGB pixels.
(Omit the CFBridgingRelease bit if you are not using ARC).
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What is the best algorithm for overriding GetHashCode?
...hroughout the .NET base class libraries. Implementing it properly is especially important to find items quickly in a collection or when determining equality.
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Principal component analysis in Python
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Months later, here's a small class PCA, and a picture:
#!/usr/bin/env python
""" a small class for Principal Component Analysis
Usage:
p = PCA( A, fraction=0.90 )
In:
A: an array of e.g. 1000 observations x 20 variables, 1000 rows x 20 colum...
How to efficiently compare two unordered lists (not sets) in Python?
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For short lists, big-O analysis is usually irrelevant because the timings are dominated by constant factors. For the longer lists, I suspect something is wrong with your benchmarking. For 100 ints with 5 repeats each, I get: 127 usec for sorted and 42 for Count...
Converting between datetime, Timestamp and datetime64
...>> numpy.__version__
'1.6.2' # current version available via pip install numpy
I can reproduce the long value on numpy-1.8.0 installed as:
pip install git+https://github.com/numpy/numpy.git#egg=numpy-dev
The same example:
>>> from datetime import datetime
>>> import num...
What is the difference between a definition and a declaration?
...// extern can be omitted for function declarations
class foo; // no extern allowed for type declarations
A definition actually instantiates/implements this identifier. It's what the linker needs in order to link references to those entities. These are definitions corresponding to the above declara...