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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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How to identify server IP address in PHP
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Like this for the server ip:
$_SERVER['SERVER_ADDR'];
and this for the port
$_SERVER['SERVER_PORT'];
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Python Linked List
...st is defined simply by '(1 2 3 4 5) . Python's lists, [1, 2, 3, 4, 5] , and tuples, (1, 2, 3, 4, 5) , are not, in fact, linked lists, and linked lists have some nice properties such as constant-time concatenation, and being able to reference separate parts of them. Make them immutable and they a...
Items in JSON object are out of order using “json.dumps”?
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Both Python dict (before Python 3.7) and JSON object are unordered collections. You could pass sort_keys parameter, to sort the keys:
>>> import json
>>> json.dumps({'a': 1, 'b': 2})
'{"b": 2, "a": 1}'
>>> json.dumps({'a': 1, 'b': 2},...
Is there a JavaScript function that can pad a string to get to a determined length?
I am in need of a JavaScript function which can take a value and pad it to a given length (I need spaces, but anything would do). I found this:
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How to escape text for regular expression in Java
...se not that this doesn’t escape the string itself, but wraps it using \Q and \E. This may lead to unexpected results, for example Pattern.quote("*.wav").replaceAll("*",".*") will result in \Q.*.wav\E and not .*\.wav, as you might expect.
– Matthias Ronge
Jan ...
Trying to understand CMTime and CMTimeMake
1) CMTimeMake(1,10) means duration of 1 second and timescale of 10, or 10 frames per second. This means 1s duration of video with 10 frames?
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Are there any O(1/n) algorithms?
...put size for which the algorithm is not supposed to execute any operation. And therefore I would think that O(1/n) time complexity is indeed impossible to achieve.
– Roland Ewald
May 25 '09 at 14:10
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How can I force WebKit to redraw/repaint to propagate style changes?
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I found some complicated suggestions and many simple ones that didn’t work, but a comment to one of them by Vasil Dinkov provided a simple solution to force a redraw/repaint that works just fine:
sel.style.display='none';
sel.offsetHeight; // no need to store...
What is a “cache-friendly” code?
What is the difference between " cache unfriendly code " and the " cache friendly " code?
9 Answers
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