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Index on multiple columns in Ruby on Rails
...at the beginning. i.e. if you index on [:user_id, :article_id], you can perform a fast query on user_id or user_id AND article_id, but NOT on article_id.
Your migration add_index line should look something like this:
add_index :user_views, [:user_id, :article_id]
Question regarding 'unique' ...
Why are empty strings returned in split() results?
...to be equal to ['segment', 'segment'] is reasonable, but then this loses information. If split() worked the way you wanted, if I tell you that a.split('/') == ['segment', 'segment'], you can't tell me what a was.
What should be the result of 'a//b'.split() be? ['a', 'b']?, or ['a', '', 'b']? I.e., ...
Parcelable where/when is describeContents() used?
...ace
Implementing multiple inheritance by rules defined in human readable form? :-)
It seems like C++ programmer designed Parceable and at some point he realized: Oh, damn, there is no multiple inheritance in Java... :-)
s...
How to write to a JSON file in the correct format
...reating a hash in Ruby and want to write it to a JSON file, in the correct format.
4 Answers
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How can I view the source code for a function?
...nv") for currently available ones.
The output already offers a lot of information. standardGeneric is an indicator of an S4 function. The method to see defined S4 methods is offered helpfully:
> showMethods(chol2inv)
Function: chol2inv (package base)
x="ANY"
x="CHMfactor"
x="denseMatrix"
x="d...
Turn off Chrome/Safari spell checking by HTML/css
...
for all elements of a form it is possible and so:
<form spellcheck="false" .. />
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Is a statically-typed full Lisp variant possible?
...te, let's take a look at the list structure itself, called the cons, which forms the primary building block of Lisp.
Calling the cons a list, though (1 2 3) looks like one, is a bit of a misnomer. For example, it's not at all comparable to a statically typed list, like C++'s std::list or Haskell's ...
What is the difference between IQueryable and IEnumerable?
...om query logic it receives, e.g., a predicate or value selector, is in the form of an expression tree instead of a delegate to a method.
IEnumerable<T> is great for working with sequences that are iterated in-memory, but
IQueryable<T> allows for out-of memory things like a remote data s...
Replacing .NET WebBrowser control with a better browser, like Chrome?
...ndows and Github for Windows.
It features browser controls for WPF and Winforms and has tons of features and extension points. Being based on Chromium it's blisteringly fast too.
Grab it from NuGet: Install-Package CefSharp.Wpf or Install-Package CefSharp.WinForms
Check out examples and give you...
Local file access with JavaScript
... restrictions. First, scripts run in a
sandbox in which they can only perform
web-related actions, not
general-purpose programming tasks like
creating files.
2016 UPDATE: Accessing the filesystem directly is possible via the Filesystem API, which is only supported by Chrome and Opera and m...