In _Ruby Programming Language_ (&quot;Methods, Procs, Lambdas, and Closures&quot;), a lambda defined using `-&gt;` is called _lambda literal_. 

    succ = -&gt;(x){ x+1 }
    succ.call(2)

The code is equivalent to the following one. 

    succ = lambda { |x| x + 1 }
    succ.call(2)

Informally, I have heard it being called _stabby lambda_ or _stabby literal_.

### `=&gt;` == **Hash Rocket**

Separates keys from values in a hash map literal.

----------

### `-&gt;` == **Dash Rocket**
Used to define a lambda literal in Ruby 1.9.X (without args) and Ruby 2.X (with args). The examples you give (`-&gt;(x) { x * 2 }` &amp; `lambda { |x| x * 2 }`) are in fact equivalent.

`-&gt;(x) { ... }` is the same as `lambda { |x| ... }`. It creates a lambda. See [Kernel#lambda](http://ruby-doc.org/core-2.5.1/Kernel.html#method-i-lambda)  A lambda is a type of proc, one that ensures the number of parameters passed to it is correct. See also [Proc::new](http://ruby-doc.org/core-2.5.1/Proc.html#method-c-new) and [Kernel#proc](http://ruby-doc.org/core-2.5.1/Kernel.html#method-i-proc).

When the BACK button is pressed on the phone, I want to prevent a specific activity from returning to its previous one.

Specifically, I have login and sign up screens, both start a new activity called `HomeScreen` when successful login/signup occurs. Once HomeScreen is started, I want to prevent the users from being able to return to the login or sign up screens by pressing the BACK key. 

I tried using `Intent.FLAG_ACTIVITY_NO_HISTORY`, but since the application has Facebook integration, when the &#39;Login with Facebook&#39; is used, Facebook should return to the initial login screen, therefore I should keep a history of these activities.

I thought of overriding the behaviour of the BACK button on `HomeScreen` to directly finish an application when the button is pressed and I used

    @Override
	public void onBackPressed() {
		finish();
	}

but that also does not work.


How to prevent going back to the previous activity?

I want to prompt the user for a series of inputs, including a password and a filename.

I have an example of using `host.ui.prompt`, which seems sensible, but I can&#39;t understand the return.

Is there a better way to get user input in PowerShell?


Prompt for user input in PowerShell

1. What do you call the `-&gt;` operator as in the following?

        -&gt;(...) do
          ...
        end

2. Aren&#39;t the following snippets equivalent?

        succ = -&gt;(x) {x + 1}
        succ = lambda {|x| x + 1}


What do you call the -&gt; operator in Ruby?

<ol>
<li>
What do you call the <code>-></code> operator as in the following?
<pre><code class="hljs language-arduino"> ->(...) do
 ...
 end
</code></pre>
</li>
<li>
Aren't the following snippets equivalent?
<pre><code class="hljs language-ini"> succ = ->(x) {x + 1}
 succ = lambda {|x| x + 1}
</code></pre>
</li>
</ol>

I&#39;m using jquery-mobile with Ruby On Rails.

I want to create a button link which implies to have `data-role=&quot;button&quot;` appear in the generated HTML. 

I&#39;ve tried:

    &lt;%= link_to &quot;Play&quot;, game_play_path, :data-role =&gt; &quot;button&quot; %&gt;

But then, I get an error

    undefined local variable or method `role&#39; for #&lt;#&lt;Class:0x007fdc25668ee8&gt;:0x007fdc25658610&gt;

Is there a way to escape the dash using the `:xxx` notation or should I just use the `&quot;xxx&quot;` notation?

(I agree it&#39;s a cosmetic question, but I want my code to be consistent and don&#39;t like exceptions)

How to escape a dash &quot;-&quot; in a Ruby symbol?

What is the difference between an it block and a specify block in RSpec?

    subject { MovieList.add_new(10) }
    
    specify { subject.should have(10).items }
    it { subject.track_number.should == 10}

They seem to do the same job. Just checking to be sure.

Difference between an it block and a specify block in RSpec

I am developing a **Ruby on Rails** app. My question is more about **Ruby** syntax. 

I have a model class with a class method `self.check`:

    class Cars &lt; ActiveRecord::Base
      ...
      def self.check(name)
         self.all.each do |car|
              #if result is true, break out from the each block, and return the car how to...
              result = SOME_CONDITION_MEET?(car) #not related with database
         end

         puts &quot;outside the each block.&quot;
      end
    end

I would like to stop/break out from the `each` block **once** the `result` is **true** (that&#39;s break the `each` block if `car.name` is the same as the `name` parameter **once**) AND return the `car` which cause the **true** result. How to break out in Ruby code?

Ruby syntax: break out from &#39;each.. do..&#39; block

AS the title says I am trying to check whether a variable is defined in SASS. (I am using compass if that makes any different difference)

I&#39;ve found the Ruby equivalent which is:

&lt;pre&gt;&lt;code&gt;defined? foo&lt;/code&gt;&lt;/pre&gt;

Gave that a shot in the dark but it just gave me the error:

`defined&quot;: expected &quot;{&quot;, was &quot;?`

I&#39;ve found a work around (which is obviously just to define the variable in all cases, which in this case it actually makes more sense) but I&#39;d really like to know if this is possible for the future



Checking if a variable is defined in SASS

I have a `public/cache` folder which has files and folders. How can I completely empty that folder using a rake task?

How to delete all contents of a folder with Ruby-Rails?

Is there any difference between `:key =&gt; &quot;value&quot;` (hashrocket) and `key: &quot;value&quot;` (Ruby 1.9) notations?

If not, then I would like to use `key: &quot;value&quot;` notation. Is there a gem that helps me to convert from `:x =&gt;` to `x:` notations?

Is there any difference between the `:key =&gt; &quot;value&quot;` and `key: &quot;value&quot;` hash notations?

I&#39;m not sure if this is a proper programming question, but it&#39;s something that has always bothered me, and I wonder if I&#39;m the only one.

When initially learning C++, I understood the concept of references, but pointers had me confused. Why, you ask? Because of how you declare a pointer.

Consider the following:

    void foo(int* bar)
    {
    }

   
    int main()
    {
	    int x = 5;
	    int* y = NULL;
	
	    y = &amp;x;
	    *y = 15;	 
        foo(y);

    }

The function `foo(int*)` takes an `int` pointer as parameter. Since I&#39;ve declared `y` as `int` pointer, I can pass `y` to `foo`, but when first learning C++ I associated the `*` symbol with dereferencing, as such I figured a dereferenced `int` needed to be passed. I would try to pass `*y` into `foo`, which obviously doesn&#39;t work.

Wouldn&#39;t it have been easier to have a separate operator for declaring a pointer? (or for dereferencing). For example:

    void test(int@ x)
    {
    }



Why is the dereference operator (*) also used to declare a pointer?

When testing for membership, we can use:

    x not in y

Or alternatively:

    not x in y

There can be many possible contexts for this expression depending on `x` and `y`.  It could be for a substring check, list membership, dict key existence, for example.

- Are the two forms always equivalent?  
- Is there a preferred syntax?


&quot;x not in y&quot; or &quot;not x in y&quot;

In shell scripts, when do we use `{}` when expanding variables?

For example, I have seen the following:

    var=10        # Declare variable

    echo &quot;${var}&quot; # One use of the variable
    echo &quot;$var&quot;   # Another use of the variable

Is there a significant difference, or is it just style? Is one preferred over the other?

When do we need curly braces around shell variables?

&gt; **Possible Duplicate:**  
&gt; [Accessing nested JavaScript objects with string key](https://stackoverflow.com/questions/6491463/accessing-nested-javascript-objects-with-string-key)  

&lt;!-- End of automatically inserted text --&gt;

Maybe the title is not clear enough, I just didn&#39;t know how to specify what I&#39;m looking for and my English is really bad, sorry.

I&#39;m trying to create function that returns object value, but also plays nice with nested objects. For example:

    var obj = {
      foo: { bar: &#39;baz&#39; }
    };

I want to access the value of obj.foo.bar by suppling the string &quot;foo.bar&quot; to the function.

    function(obj, path) {
      // Path can be &quot;foo.bar&quot;, or just &quot;foo&quot;.
    }

Thanks!

Content Type	Original Author	Original Content on Stackoverflow
Question	Matt - sanemat	View Question on Stackoverflow
Solution 1 - Ruby	apaderno	View Answer on Stackoverflow
Solution 2 - Ruby	Yarin	View Answer on Stackoverflow
Solution 3 - Ruby	Cary Swoveland	View Answer on Stackoverflow

What do you call the -> operator in Ruby?

Ruby Problem Overview

Ruby Solutions

Solution 1 - Ruby

Solution 2 - Ruby

`=>` == Hash Rocket

`->` == Dash Rocket

Solution 3 - Ruby

Prompt for user input in PowerShell

How to prevent going back to the previous activity?

Attributions

Ruby Problem Overview

Ruby Solutions

Solution 1 - Ruby

Solution 2 - Ruby

=> == Hash Rocket

-> == Dash Rocket

Solution 3 - Ruby

Prompt for user input in PowerShell

How to prevent going back to the previous activity?

Attributions

`=>` == Hash Rocket

`->` == Dash Rocket