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How to add column if not exists on PostgreSQL?
Question is simple. How to add column x to table y , but only when x column doesn't exist ? I found only solution here how to check if column exists.
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Position of least significant bit that is set
...position of the least significant bit that is set in an integer, e.g. for 0x0FF0 it would be 4.
22 Answers
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How does deriving work in Haskell?
...se to implement it in its own way. There's lots of work on how to make it extensible however.
Derive is a tool for Haskell to let you write your own deriving mechanisms.
GHC used to provide a derivable type class extension called Generic Classes, but it was rarely used, as it was somewhat weak.
Th...
how to remove untracked files in Git?
I'm working on a branch, say "experimental" branch which I branch out from my master branch.Then, I generate a user model in experimental branch, but does not add them to index yet.
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What is in your .vimrc? [closed]
...ed inside a .vimrc file. Typical features for a programmer would be syntax highlighting, smart indenting and so on.
72 An...
How can I add numbers in a Bash script?
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For integers:
Use arithmetic expansion: $((EXPR))
num=$((num1 + num2))
num=$(($num1 + $num2)) # Also works
num=$((num1 + 2 + 3)) # ...
num=$[num1+num2] # Old, deprecated arithmetic expression syntax
Using the external expr utili...
How to convert a color integer to a hex String in Android?
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The mask makes sure you only get RRGGBB, and the %06X gives you zero-padded hex (always 6 chars long):
String hexColor = String.format("#%06X", (0xFFFFFF & intColor));
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Fatal error: “No Target Architecture” in Visual Studio
... try to compile my c++ project using Visual Studio 2010 in either Win32 or x64 mode I get the following error:
11 Answers
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Apache Prefork vs Worker MPM
...tion at a time// here connection means single user or single request? pls explain
– user1844933
Jun 25 '19 at 7:18
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Access multiple elements of list knowing their index
I need to choose some elements from the given list, knowing their index. Let say I would like to create a new list, which contains element with index 1, 2, 5, from given list [-2, 1, 5, 3, 8, 5, 6]. What I did is:
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