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What's the difference between HEAD^ and HEAD~ in Git?
When I specify an ancestor commit object in Git, I'm confused between HEAD^ and HEAD~ .
15 Answers
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What's the difference between array_merge and array + array?
A fairly simple question. What's the difference between:
9 Answers
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C++ equivalent of java's instanceof
...>doSomething();
}
This requires your compiler to have rtti support enabled.
EDIT:
I've had some good comments on this answer!
Every time you need to use a dynamic_cast (or instanceof) you'd better ask yourself whether it's a necessary thing. It's generally a sign of poor design.
Typical wor...
Combine the first two commits of a Git repository?
Suppose you have a history containing the three commits A, B and C :
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Relationship between SciPy and NumPy
SciPy appears to provide most (but not all [1]) of NumPy's functions in its own namespace. In other words, if there's a function named numpy.foo , there's almost certainly a scipy.foo . Most of the time, the two appear to be exactly the same, oftentimes even pointing to the same function object.
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LINQ Aggregate algorithm explained
This might sound lame, but I have not been able to find a really good explanation of Aggregate .
12 Answers
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Why do I need 'b' to encode a string with Base64?
Following this python example , I encode a string as Base64 with:
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Convert columns to string in Pandas
... your keys to strings):
In [11]: df = pd.DataFrame([['A', 2], ['A', 4], ['B', 6]])
In [12]: df.to_json()
Out[12]: '{"0":{"0":"A","1":"A","2":"B"},"1":{"0":2,"1":4,"2":6}}'
In [13]: df[0].to_json()
Out[13]: '{"0":"A","1":"A","2":"B"}'
Note: you can pass in a buffer/file to save this to, along wi...
Many-to-many relationship with the same model in rails?
...itional information with the association? (Additional fields in the join table.)
Do the associations need to be implicitly bi-directional?
(If post A is connected to post B, then post B is also connected to post A.)
That leaves four different possibilities. I'll walk over these below.
For referen...
Apply multiple functions to multiple groupby columns
The docs show how to apply multiple functions on a groupby object at a time using a dict with the output column names as the keys:
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