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How to specialize std::hash::operator() for user-defined type in unordered containers?
To support user-defined key types in std::unordered_set<Key> and std::unordered_map<Key, Value>
one has to provide operator==(Key, Key) and a hash functor:
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What is the difference between Gemfile and Gemfile.lock in Ruby on Rails
I am a beginner to Ruby on Rails and I am using Rails 3.0.9.
3 Answers
3
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What is the difference between Numpy's array() and asarray() functions?
...() functions? When should you use one rather than the other? They seem to generate identical output for all the inputs I can think of.
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mongoDB/mongoose: unique if not null
I was wondering if there is way to force a unique collection entry but only if entry is not null .
e
Sample schema:
4 Answ...
Is it intended by the C++ standards committee that in C++11 unordered_map destroys what it inserts?
I've just lost three days of my life tracking down a very strange bug where unordered_map::insert() destroys the variable you insert. This highly non-obvious behaviour occurs in very recent compilers only: I found that clang 3.2-3.4 and GCC 4.8 are the only compilers to demonstrate this "feature"....
How to get a pixel's x,y coordinate color from an image?
Is there any way to check if a selected(x,y) point of a PNG image is transparent?
4 Answers
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Why do we need a pure virtual destructor in C++?
...e virtual destructors are allowed is that to prohibit them would mean adding another rule to the language and there's no need for this rule since no ill-effects can come from allowing a pure virtual destructor.
Nope, plain old virtual is enough.
If you create an object with default implementation...
C++ Tuple vs Struct
Is there is any difference between using a std::tuple and a data-only struct ?
12 Answers
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Android: AsyncTask vs Service
...nswer to most questions here a lot about AsyncTask and Loaders but nothing about Services ? Are Services just not known very well or are they deprecated or have some bad attributes or something? What are the differences?
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“Diff” an image using ImageMagick
How can I get the difference between two images? I have the original image. Someone has written on an exact duplicate of the original image. Now, I need to compare the original to the written on image and extract just the writing in image format.
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