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Simultaneously merge multiple data.frames in a list
...o merge. The issue here is that each data.frame differs in terms of the number of rows and columns, but they all share the key variables (which I've called "var1" and "var2" in the code below). If the data.frames were identical in terms of columns, I could merely rbind , for which plyr's rbind...
Math - mapping numbers
How do I map numbers, linearly, between a and b to go between c and d.
9 Answers
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How are the points in CSS specificity calculated
Researching specificity I stumbled upon this blog - http://www.htmldog.com/guides/cssadvanced/specificity/
7 Answers
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git rebase, keeping track of 'local' and 'remote'
When doing a git rebase, I often have difficulty working out what is happening with the 'local' and 'remote' when resolving conflicts. I sometimes have the impression that they swap sides from one commit to the next.
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Where does 'Hello world' come from?
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Brian Kernighan actually wrote the first "hello, world" program as part of the documentation for the BCPL programming language developed by Martin Richards. BCPL was used while C was being developed at Bell Labs a few years b...
How to make an immutable object in Python?
Although I have never needed this, it just struck me that making an immutable object in Python could be slightly tricky. You can't just override __setattr__ , because then you can't even set attributes in the __init__ . Subclassing a tuple is a trick that works:
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Why isn't vector a STL container?
Item 18 of Scott Meyers's book Effective STL: 50 Specific Ways to Improve Your Use of the Standard Template Library says to avoid vector <bool> as it's not an STL container and it doesn't really hold bool s.
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How is Math.Pow() implemented in .NET Framework?
I was looking for an efficient approach for calculating a b (say a = 2 and b = 50 ). To start things up, I decided to take a look at the implementation of Math.Pow() function. But in .NET Reflector , all I found was this:
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What is a Context Free Grammar?
... then the Wikipedia entry on formal grammar, I am left utterly and totally befuddled. Would someone be so kind as to explain what these things are?
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Explicit vs implicit SQL joins
...Performance wise, they are exactly the same (at least in SQL Server).
PS: Be aware that the IMPLICIT OUTER JOIN syntax is deprecated since SQL Server 2005. (The IMPLICIT INNER JOIN syntax as used in the question is still supported)
Deprecation of "Old Style" JOIN Syntax: Only A Partial Thing
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