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Is there a literal notation for an array of symbols?
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Yes! This is possible now in Ruby 2.0.0. One way to write it is:
%i{foo bar} # => [:foo, :bar]
You can also use other delimiters, so you could also write %i(foo bar) or %i!foo bar! for example.
This feature was originally announced here:
http://www.ruby-lang.org/zh_TW/news/2012/11/02/...
How to get a list of column names on Sqlite3 database?
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PRAGMA table_info(table_name);
will get you a list of all the column names.
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Given a class, see if instance has method (Ruby)
...d
then read this:
In Ruby, a property (attribute) on your model is basically a method also. So method_defined? will also return true for properties, not just methods.
For example:
Given an instance of a class that has a String attribute first_name:
<instance>.first_name.class #=> Stri...
How to convert a PIL Image into a numpy array?
...to a numpy array this way:
import numpy
import PIL
img = PIL.Image.open("foo.jpg").convert("L")
imgarr = numpy.array(img)
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Determine .NET Framework version for dll
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This answer is the most helpful. All Windows OSes after 2003 support Powershell. A shell giving immediate feedback, not requiring any additional application support as many of the other answers suggest. Great for a "one off" check of a dll. you're the man @...
What is the proper way to check if a string is empty in Perl?
... situation where you haven't already guarded against undef, then the catch-all for "non-empty" that won't warn is if (defined $str and length $str).
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How do I compare strings in Java?
I've been using the == operator in my program to compare all my strings so far.
However, I ran into a bug, changed one of them into .equals() instead, and it fixed the bug.
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ignoring any 'bin' directory on a git project
... mean zero or more sub-directories (see release notes).
The way to ignore all directories called bin anywhere below the current level in a directory tree is with a .gitignore file with the pattern:
bin/
In the man page, there an example of ignoring a directory called foo using an analogous patte...
Expression Versus Statement
...as one unit of execution, a thing that you did. The only reason it wasn't called a "line" was because sometimes it spanned multiple lines. An expression on its own couldn't do anything... you had to assign it to a variable.
1 + 2 / X
is an error in FORTRAN, because it doesn't do anything. You had...
What is the Swift equivalent of -[NSObject description]?
...scription.
For example:
class MyClass: CustomStringConvertible {
let foo = 42
var description: String {
return "<\(type(of: self)): foo = \(foo)>"
}
}
print(MyClass()) // prints: <MyClass: foo = 42>
Note: type(of: self) gets the type of the current instances ins...