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How do I calculate the normal vector of a line segment?
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if we define dx=x2-x1 and dy=y2-y1, then the normals are (-dy, dx) and (dy, -dx).
Note that no division is required, and so you're not risking dividing by zero.
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Difference between Dictionary and Hashtable [duplicate]
What is the difference between Dictionary and Hashtable. How to decide which one to use?
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What's the difference between “squash” and “fixup” in Git/Git Extension?
...the commit log message begins with "squash! ..." (or "fixup!
..."), and there is a commit whose title begins with the same ...,
automatically modify the todo list of rebase -i so that the commit
marked for squashing comes right after the commit to be modified,
and change ...
How do I ignore a directory with SVN?
I just started using SVN, and I have a cache directory that I don't need under source control. How can I ignore the whole directory/folder with SVN?
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Is there a ceiling equivalent of // operator in Python?
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There is no operator which divides with ceil. You need to import math and use math.ceil
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Retrieve the position (X,Y) of an HTML element relative to the browser window
I want to know how to get the X and Y position of HTML elements such as img and div in JavaScript relative to the browser window.
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Will strlen be calculated multiple times if used in a loop condition?
...tion. If it might, then you'll need to either call strlen() each time, or handle it through more complicated logic.
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Why covariance and contravariance do not support value type
...or not.
You might want to read Eric Lippert's blog post on representation and identity for more on this topic in general.
EDIT: Having reread Eric's blog post myself, it's at least as much about identity as representation, although the two are linked. In particular:
This is why covariant and ...
parseInt(null, 24) === 23… wait, what?
Alright, so I was messing around with parseInt to see how it handles values not yet initialized and I stumbled upon this gem. The below happens for any radix 24 or above.
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What Makes a Method Thread-safe? What are the rules?
...ere overall rules/guidelines for what makes a method thread-safe? I understand that there are probably a million one-off situations, but what about in general? Is it this simple?
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