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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 execute a raw update sql with dynamic binding in rails
... to do this generically. You could try accessing the underlying connection and using it's methods, e.g. for MySQL:
st = ActiveRecord::Base.connection.raw_connection.prepare("update table set f1=? where f2=? and f3=?")
st.execute(f1, f2, f3)
st.close
I'm not sure if there are other ramifications t...
Method to Add new or update existing item in Dictionary
... indexer setters of both classes call this.Insert(key, value, add: false); and the add parameter is responsible for throwing an exception, when inserting a duplicate key. So the behavior is the same for both classes.
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How to test code dependent on environment variables using JUnit?
I have a piece of Java code which uses an environment variable and the behaviour of the code depends on the value of this variable. I would like to test this code with different values of the environment variable. How can I do this in JUnit?
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Use of the MANIFEST.MF file in Java
I noticed that JAR, WAR and EAR files have a MANIFEST.MF file under the META-INF folder.
2 Answers
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Git pull after forced update
I just squashed some commits with git rebase and did a git push --force (which is evil, I know).
3 Answers
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Java system properties and environment variables
What's the difference between system properties System.getProperties() and environment variables System.getenv() in a JVM?
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Failed to Attach to Process ID Xcode
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Resetting the content and settings in the simulator worked for me. This is available in the "iOS Simulator" menu.
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MySQL selecting yesterday's date
How can I display and count the values whose dates are yesterday?
I used time() to insert date in the database. Example:
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Eclipse - “Workspace in use or cannot be created, chose a different one.” [duplicate]
... workspace between users. The problem is that after I create the workspace and change the permission on it, I encounter the error below (image) without even switching to a different user.
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