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Thread-safe List property
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ConcurrentBag doesn't implement IList and is not actually thread safe version of List
– Vasyl Zvarydchuk
Apr 3 '17 at 20:55
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subtle differences between JavaScript and Lua [closed]
...= operators are of lower precedence than >, >=, <, <=. In Lua, all comparison operators are the same precedence.
Lua supports tail calls.
UPDATE: JS now supports tail calls.
Lua supports assignment to a list of variables. While it isn't yet standard in Javascript, Mozilla's JS engine ...
Best way to replace multiple characters in a string?
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Replacing two characters
I timed all the methods in the current answers along with one extra.
With an input string of abc&def#ghi and replacing & -> \& and # -> \#, the fastest way was to chain together the replacements like this: text.rep...
Error: No default engine was specified and no extension was provided
...err }); lines in your code with:
res.json({ error: err })
PS: People usually also have message in the returned object:
res.status(err.status || 500);
res.json({
message: err.message,
error: err
});
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Find out how much memory is being used by an object in Python [duplicate]
...and internal structures related to object types and garbage collection. Finally, some python objects have non-obvious behaviors. For instance, lists reserve space for more objects than they have, most of the time; dicts are even more complicated since they can operate in different ways (they have a ...
What is the difference between single and double quotes in SQL?
...d to indicate the beginning and end of a string in SQL. Double quotes generally aren't used in SQL, but that can vary from database to database.
Stick to using single quotes.
That's the primary use anyway. You can use single quotes for a column alias — where you want the column name you referen...
How can I use numpy.correlate to do autocorrelation?
...olution, C(t)=∑ -∞ < i < ∞ aivt+i where -∞ < t < ∞, allows for results from -∞ to ∞, but you obviously can't store an infinitely long array. So it has to be clipped, and that is where the mode comes in. There are 3 different modes: full, same, & valid:
"full" mode r...
*.h or *.hpp for your class definitions
...ss definitions, but after reading some boost library code, I realised they all use *.hpp . I've always had an aversion to that file extension, I think mainly because I'm not used to it.
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Why can't I use the 'await' operator within the body of a lock statement?
The await keyword in C# (.NET Async CTP) is not allowed from within a lock statement.
8 Answers
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Rails 4 multiple image or file upload using carrierwave
...tiple_image_upload_carrierwave
In gem file
gem 'carrierwave'
bundle install
rails generate uploader Avatar
Create post scaffold
rails generate scaffold post title:string
Create post_attachment scaffold
rails generate scaffold post_attachment post_id:integer avatar:string
rake db:migrate
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