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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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Is there a “do … until” in Python? [duplicate]
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BTW, this is called "loop-and-a-half". Python continues to support this construct because it's one of the easiest loop patterns to correctly write and understand. See cs.duke.edu/~ola/patterns/plopd/loops.html#loop-and-a-half
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How do I update a Python package?
I'm running Ubuntu 9:10 and a package called M2Crypto is installed (version is 0.19.1). I need to download, build and install the latest version of the M2Crypto package (0.20.2).
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How to do an update + join in PostgreSQL?
... -- joined table
WHERE
a.abiturient_id = b.id AND -- JOIN ON clause
a.documents_taken_at::date < b.certificate_issued_at -- Subquery WHERE
As you can see, original subquery JOIN's ON clause have become one of WHERE conditions, which is ...
Custom UITableViewCell from nib in Swift
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With Swift 5 and iOS 12.2, you should try the following code in order to solve your problem:
CustomCell.swift
import UIKit
class CustomCell: UITableViewCell {
// Link those IBOutlets with the UILabels in your .XIB file
@IBOutl...
Detecting arrow key presses in JavaScript
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@MrCroft - or also listen to onkeyup and stop the event there. Realistically you shouldn't be modifying UI behavior with Javascript, however.
– Mark Kahn
Jan 5 '17 at 19:52
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Determine if a function exists in bash
...t tests which are executed from bash. Unit tests are initialized, executed and cleaned up in a bash script. This script usualy contains an init(), execute() and cleanup() functions. But they are not mandatory. I'd like to test if they are or are not defined.
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Is it good practice to use java.lang.String.intern()?
... that you're going to compare. It's easy to forget to intern() all strings and then you can get confusingly incorrect results. Also, for everyone's sake, please be sure to very clearly document that you're relying on the strings being internalized.
The second disadvantage if you decide to internali...
How to align input forms in HTML
I'm new to HTML and I'm trying to learn how to use forms.
16 Answers
16
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SQL Server Operating system error 5: “5(Access is denied.)”
I am starting to learn SQL and I have a book that provides a database to work on. These files below are in the directory but the problem is that when I run the query, it gives me this error:
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