### What is this?

This is a collection of questions that come up every now and then about syntax in PHP. This is also a Community Wiki, so everyone is invited to participate in maintaining this list. 

### Why is this?

It used to be hard to find questions about operators and other syntax tokens.&#185;  
The main idea is to have links to existing questions on Stack Overflow, so it&#39;s easier for us to reference them, not to copy over content from the PHP Manual.

Note: Since January 2013, Stack Overflow [does support special characters][1]. Just surround the search terms by quotes, e.g. [`[php] &quot;==&quot; vs &quot;===&quot;`][2]

### **What should I do here?**

If you have been pointed here by someone because you have asked such a question, please find the particular syntax below. The linked pages to the [PHP manual](http://php.net/manual/en/index.php) along with the linked questions will likely answer your question then. If so, you are encouraged to upvote the answer. This list is not meant as a substitute for the help others provided.

## The List

If your particular token is not listed below, you might find it in the [List of Parser Tokens][3].

---

`&amp;` [Bitwise Operators][4] or [References][5]

 - https://stackoverflow.com/questions/1676897
 - https://stackoverflow.com/questions/600202
 - https://stackoverflow.com/questions/2209934/
 - https://stackoverflow.com/questions/2376348
 - https://stackoverflow.com/questions/1006652
 - https://stackoverflow.com/questions/2297592
 - https://stackoverflow.com/questions/2422907
 - https://stackoverflow.com/questions/2478149
 - https://stackoverflow.com/questions/3957584
 - https://stackoverflow.com/questions/4705262
 - https://stackoverflow.com/questions/4705838
 - https://stackoverflow.com/questions/21058439 (&amp;$)

---

`=&amp;` [References][5]

 - https://stackoverflow.com/questions/1768343
 - https://stackoverflow.com/questions/1367454
 - https://stackoverflow.com/questions/3177342
 - https://stackoverflow.com/questions/2081806

---

`&amp;=` [Bitwise Operators][4]

 - https://stackoverflow.com/questions/1367454
 - https://stackoverflow.com/questions/3177342

---

`&amp;&amp;` [Logical Operators][6]

 - https://stackoverflow.com/questions/2803321
 - https://stackoverflow.com/questions/2376348
 - https://stackoverflow.com/questions/4746865
 - https://stackoverflow.com/questions/4502092

---

`%` [Arithmetic Operators][7]

 - https://stackoverflow.com/questions/1934173
 - https://stackoverflow.com/questions/3204919

---

`!!` [Logical Operators][6]

 - https://stackoverflow.com/questions/2127260

---

`@` [Error Control Operators][8]

 - https://stackoverflow.com/questions/1032161
 - https://stackoverflow.com/questions/3551527
 - https://stackoverflow.com/questions/3984864
 - https://stackoverflow.com/questions/4872340
 - https://stackoverflow.com/questions/3621215

---

`?:` [Ternary Operator][9]

 - https://stackoverflow.com/questions/1080247
 - https://stackoverflow.com/questions/1993409
 - https://stackoverflow.com/questions/4055355
 - https://stackoverflow.com/questions/4210187

---

`??` [Null Coalesce Operator][36] (since PHP 7)

 - https://stackoverflow.com/questions/7278835

---

`?string`
`?int`
`?array`
`?bool`
`?float` [Nullable return type declaration][10] (since PHP 7.1)

 - [Nullable return type declaration](https://stackoverflow.com/a/54217328/250259)
 - [Nullable parameter type declaration](https://stackoverflow.com/a/48450841)
 - [php method argument type hinting with question mark (?type)][34]

---

`:` [Alternative syntax for control structures][11], [Ternary Operator][9], [Return Type Declaration](https://www.php.net/manual/en/language.types.declarations.php)

 - https://stackoverflow.com/questions/2908095
 - https://stackoverflow.com/questions/4747761
 - https://stackoverflow.com/questions/40346754

---

`::` [Scope Resolution Operator][12]

 - https://stackoverflow.com/questions/2903564
 - https://stackoverflow.com/questions/2588298
 - https://stackoverflow.com/questions/3173501
 - https://stackoverflow.com/questions/1912902
 - https://stackoverflow.com/questions/4120755
 - https://stackoverflow.com/questions/8734823

---

`\` [Namespaces][13]

 - https://stackoverflow.com/questions/10788400
 - https://stackoverflow.com/questions/4790020

---

`-&gt;` [Classes And Objects][14]

 - https://stackoverflow.com/questions/2588149
 - https://stackoverflow.com/questions/3037526
 - https://stackoverflow.com/questions/3173501
 - https://stackoverflow.com/questions/2316370
 - https://stackoverflow.com/questions/4502587

---

`=&gt;` [Arrays][15]

 - https://stackoverflow.com/questions/1241819
 - https://stackoverflow.com/questions/1655336
 - https://stackoverflow.com/questions/4758791

---

`^` [Bitwise Operators][4]

 - https://stackoverflow.com/questions/2674920
 - https://stackoverflow.com/questions/2724936

---

`&gt;&gt;` [Bitwise Operators][4]

 - https://stackoverflow.com/questions/2790329

---

`&lt;&lt;` [Bitwise Operators][4]

- https://stackoverflow.com/questions/9718689/strange-print-behaviour-in-php

---

`&lt;&lt;&lt;` [Heredoc or Nowdoc][16]

 - https://stackoverflow.com/questions/5539669
 - https://stackoverflow.com/questions/1048481
 - https://stackoverflow.com/questions/3700042
 - https://stackoverflow.com/questions/2090081
 - https://stackoverflow.com/questions/2333779

---

`=` [Assignment Operators][17]

 - https://stackoverflow.com/questions/2063480

---

`==` [Comparison Operators][18]

 - https://stackoverflow.com/questions/80646
 - https://stackoverflow.com/questions/1663451
 - https://stackoverflow.com/questions/2063480
 - https://stackoverflow.com/questions/15813490/

---

`===` [Comparison Operators][18]

 - https://stackoverflow.com/questions/1117967
 - https://stackoverflow.com/questions/80646
 - https://stackoverflow.com/questions/2063480
 - https://stackoverflow.com/questions/15813490/

---

`!==` [Comparison Operators][18]

 - https://stackoverflow.com/questions/1298083
 - https://stackoverflow.com/questions/1139154

---

`!=` [Comparison Operators][18]

 - https://stackoverflow.com/questions/1663451
 - https://stackoverflow.com/questions/1139154
 - https://stackoverflow.com/questions/6356826
 - https://stackoverflow.com/questions/9671785/what-is-the-difference-between-and

---

`&lt;&gt;` [Comparison Operators][18]

 - https://stackoverflow.com/questions/249312
 - https://stackoverflow.com/questions/589391
 - https://stackoverflow.com/questions/9671785
 - https://stackoverflow.com/questions/15813490/

---

`&lt;=&gt;` [Comparison Operators][18] (since PHP 7.0)

 - [Spaceship (three way comparison) operator][19]

---

`|` [Bitwise Operators][4]

 - https://stackoverflow.com/questions/2233835
 - https://stackoverflow.com/questions/13811922

---

`||` [Logical Operators][6]

 - https://stackoverflow.com/questions/2233835
 - https://stackoverflow.com/questions/4502092
 - https://stackoverflow.com/questions/5666741
 - https://stackoverflow.com/questions/12213283

---

`~` [Bitwise Operators][4]

 - https://stackoverflow.com/questions/1967360

---

`+` [Arithmetic Operators][7], [Array Operators][20]

 - https://stackoverflow.com/questions/2140090

---

`+=` and `-=` [Assignment Operators][17]

 - https://stackoverflow.com/questions/542995
 - https://stackoverflow.com/questions/7140158

---

`++` and `--` [Incrementing/Decrementing Operators][21]

 - https://stackoverflow.com/questions/1968371
 - [Answer below][22]

---

`.=` [Assignment Operators][17]

 - https://stackoverflow.com/questions/2202331
 - https://stackoverflow.com/questions/1241432

---

`.` [String Operators][23]

 - https://stackoverflow.com/questions/1466408
 - https://stackoverflow.com/questions/6484968

---

`,` [Function Arguments][24]

 - https://stackoverflow.com/questions/1466408

`,` [Variable Declarations][25]

 - https://stackoverflow.com/questions/41383218

---

`$$` [Variable Variables][26]

 - https://stackoverflow.com/questions/2715654
 - https://stackoverflow.com/questions/4169882
 - https://stackoverflow.com/questions/4891872

---

`` ` `` [Execution Operator][27]

 - https://stackoverflow.com/questions/6002296

---

`&lt;?=` [Short Open Tags][28]

 - https://stackoverflow.com/questions/1963901
 - https://stackoverflow.com/questions/2020445
 - https://stackoverflow.com/questions/1959256/what-does-mean

---

`[]` [Arrays][15] (short syntax since PHP 5.4)

 - https://stackoverflow.com/q/20709055/2758197
 - https://stackoverflow.com/questions/6933345
 - https://stackoverflow.com/questions/2431629
 - https://stackoverflow.com/questions/3908576
 - [Shorthand for arrays: literal `$var = []` empty array](https://stackoverflow.com/questions/4271874)


---

`&lt;?` [Opening and Closing tags][29]

 - https://stackoverflow.com/questions/200640


---

`...` [Argument unpacking][30] (since PHP 5.6)

---
`**` [Exponentiation][31] (since PHP 5.6)

---
`#` [One-line shell-style comment][32]

 - [Can I use hashes for comments in PHP?][33]

---
`?-&gt;` [NullSafe Operator Calls][35] (since PHP 8.0)

- https://stackoverflow.com/questions/62178354/what-does-this-symbol-mean-in-php-within-an-object-or-null-value

---


  [1]: https://meta.stackexchange.com/questions/160100/a-new-search-engine-for-stack-exchange
  [2]: https://stackoverflow.com/search?q=%5Bphp%5D%20%22===%22%20vs%20%22==%22
  [3]: http://secure.php.net/manual/en/tokens.php
  [4]: http://secure.php.net/manual/en/language.operators.bitwise.php
  [5]: http://secure.php.net/manual/en/language.references.php
  [6]: http://secure.php.net/manual/en/language.operators.logical.php
  [7]: http://secure.php.net/manual/en/language.operators.arithmetic.php
  [8]: http://secure.php.net/manual/en/language.operators.errorcontrol.php
  [9]: http://php.net/manual/en/language.operators.comparison.php#language.operators.comparison.ternary
  [10]: https://www.php.net/manual/en/migration71.new-features.php
  [11]: http://secure.php.net/manual/en/control-structures.alternative-syntax.php
  [12]: http://secure.php.net/manual/en/language.oop5.paamayim-nekudotayim.php
  [13]: http://php.net/namespaces
  [14]: http://secure.php.net/manual/en/language.oop5.php
  [15]: http://secure.php.net/manual/en/language.types.array.php
  [16]: http://php.net/manual/en/language.types.string.php#language.types.string.syntax.heredoc
  [17]: http://secure.php.net/manual/en/language.operators.assignment.php
  [18]: http://secure.php.net/manual/en/language.operators.comparison.php
  [19]: https://stackoverflow.com/a/31298778
  [20]: http://secure.php.net/manual/en/language.operators.array.php
  [21]: http://secure.php.net/manual/en/language.operators.increment.php
  [22]: https://stackoverflow.com/a/3737177
  [23]: http://secure.php.net/manual/en/language.operators.string.php
  [24]: http://php.net/manual/en/functions.arguments.php
  [25]: http://php.net/manual/en/language.variables.scope.php
  [26]: http://php.net/manual/en/language.variables.variable.php
  [27]: http://php.net/manual/en/language.operators.execution.php
  [28]: http://php.net/manual/en/ini.core.php#ini.short-open-tag
  [29]: http://secure.php.net/manual/en/language.basic-syntax.php
  [30]: http://php.net/manual/en/functions.arguments.php#functions.variable-arg-list
  [31]: http://secure.php.net/manual/en/migration56.new-features.php#migration56.new-features.exponentiation
  [32]: http://php.net/manual/en/language.basic-syntax.comments.php
  [33]: https://stackoverflow.com/questions/9093609/can-i-use-hashes-for-comments-in-php
  [34]: https://stackoverflow.com/questions/48881489/php-method-argument-type-hinting-with-question-mark-type
  [35]: https://stackoverflow.com/a/62178856/250259
  [36]: https://www.php.net/manual/en/migration70.new-features.php#migration70.new-features.null-coalesce-op

Reference — What does this symbol mean in PHP?

I&#39;m looking for a **HTML** or **ASCII** character which is a triangle pointing up or down so that I can use it as a toggle switch.

I found &amp;uarr; (`&amp;uarr;`), and &amp;darr; (`&amp;darr;`) - but those have a narrow stem. I&#39;m looking just for the HTML arrow &quot;head&quot;.

What characters can be used for up/down triangle (arrow without stem) for display in HTML?

So I am trying to start an assignment, my professor gives us a Main.cpp, Main.h, Scanner.cpp, Scanner.h, and some other utilities.

My job is to create a Similarity class to compare documents using the cosine and Jaccard coefficients. However, I can not seem to get the project linked correctly, therefore I am unable to start on the actual code.

After trying for several hours to see what I am doing wrong, I need fresh eyes to see what I am doing wrong, I suspect it is obvious.

Here is the Main.cpp

    #include &quot;Main.h&quot;
    
    using namespace std;
    
    static const string TAG = &quot;Main: &quot;;
    
    int main(int argc, char *argv[])
    {
      string inStreamName;
      string logStreamName;
      string outStreamName;
    
      ofstream outStream;
      string timeCallOutput;
      Scanner inStream;
    
      Similarity similarity;
    
      ///////////////////////////////////////////////////////////////
      // Boilerplate for naming files and opening files
      Utils::CheckArgs(3, argc, argv, &quot;infilename outfilename logfilename&quot;);
      outStreamName = static_cast&lt;string&gt;(argv[2]);
      logStreamName = static_cast&lt;string&gt;(argv[3]);
    
      Utils::FileOpen(outStream, outStreamName);
      Utils::LogFileOpen(logStreamName);
    
      timeCallOutput = Utils::timecall(&quot;beginning&quot;);
      Utils::logStream &lt;&lt; timeCallOutput &lt;&lt; endl;
      Utils::logStream &lt;&lt; TAG &lt;&lt; &quot;Beginning execution&quot; &lt;&lt; endl;
    
      Utils::logStream &lt;&lt; TAG &lt;&lt; &quot;outfile &#39;&quot; &lt;&lt; outStreamName &lt;&lt; &quot;&#39;&quot; &lt;&lt; endl;
      Utils::logStream &lt;&lt; TAG &lt;&lt; &quot;logfile &#39;&quot; &lt;&lt; logStreamName &lt;&lt; &quot;&#39;&quot; &lt;&lt; endl;
      Utils::logStream.flush();
    
      ///////////////////////////////////////////////////////////////
      // What follows here is the real work of this code.
      //   read the entire input file and echo it back
      //   compute the two similarity coefficients
    
      inStreamName = static_cast&lt;string&gt;(argv[1]);
      inStream.openFile(inStreamName);
      Utils::logStream &lt;&lt; TAG &lt;&lt; &quot;infile &#39;&quot; &lt;&lt; inStreamName &lt;&lt; &quot;&#39;&quot; &lt;&lt; endl;
      Utils::logStream.flush();
    
      similarity.readData(inStream);
    
      outStream &lt;&lt; TAG &lt;&lt; &quot;Data Begin\n&quot; &lt;&lt; similarity.toString() &lt;&lt; endl;
      outStream &lt;&lt; TAG &lt;&lt; &quot;Data End\n&quot; &lt;&lt; endl;
      outStream.flush();
      inStream.close();
    
      outStream &lt;&lt; TAG &lt;&lt; &quot;Begin similarity computation&quot; &lt;&lt; endl;
      outStream &lt;&lt; TAG &lt;&lt; &quot;Maximum Jaccard similarity:\n&quot; &lt;&lt;
                           similarity.maxJaccard() &lt;&lt; endl;
      outStream &lt;&lt; TAG &lt;&lt; &quot;Maximum cosine similarity:\n&quot; &lt;&lt;
                           similarity.maxCosine() &lt;&lt; endl;
      outStream &lt;&lt; TAG &lt;&lt; &quot;End similarity computation&quot; &lt;&lt; endl;
      outStream.flush();
    
      ///////////////////////////////////////////////////////////////
      // Boilerplate for terminating gracefully
      Utils::logStream &lt;&lt; TAG &lt;&lt; &quot;Ending execution&quot; &lt;&lt; endl;
      timeCallOutput = Utils::timecall(&quot;ending&quot;);
      Utils::logStream &lt;&lt; timeCallOutput &lt;&lt; endl;
      Utils::logStream.flush();
    
      outStream.flush();
      Utils::FileClose(outStream);
    
      Utils::FileClose(Utils::logStream);
    
      return 0;
    }
And the Main.h

    #ifndef MAIN_H
    #define MAIN_H
    
    #include &quot;../../Utilities/Utils.h&quot;
    #include &quot;../../Utilities/Scanner.h&quot;
    
    #include &quot;Similarity.h&quot;
    
    class Main
    {
    public:
      int main();
      virtual ~Main();
    
    private:
    
    };
    
    #endif // MAIN_H

My Similarity.cpp

    #include &quot;Similarity.h&quot;
    
    using namespace std;
    
    void readData(Scanner&amp; inStream){
    }
    
    string maxCosine(){
    	return &quot;cosine&quot;;
    }
    
    string maxJaccard(){
    	return &quot;jaccard&quot;;
    }
    
    string toString(){
    	return &quot;toString&quot;;
    }

And finally my Similarity.h:

    #ifndef SIMILARITY_H
    #define SIMILARITY_H
    
    #include &quot;../../Utilities/Scanner.h&quot;
    
    class Similarity
    {
    public:
    	Similarity();
    	virtual ~Similarity();
    
    	void readData(Scanner&amp; inStream);
    	string maxCosine();
    	string maxJaccard();
    	string toString();
    private:
    
    };
    
    #endif

When I use the makefile he provided, and the one I have to use in order for his script to work to grade it I get this error:

    g++ -O3 -Wall -o Similarity.o -c Similarity.cpp
    g++ -O3 -Wall -o Aprog Main.o Similarity.o Scanner.o ScanLine.o Utils.o 
    Undefined symbols for architecture x86_64:
      &quot;Similarity::maxJaccard()&quot;, referenced from:
          _main in Main.o
      &quot;Similarity::readData(Scanner&amp;)&quot;, referenced from:
          _main in Main.o
      &quot;Similarity::toString()&quot;, referenced from:
          _main in Main.o
      &quot;Similarity::maxCosine()&quot;, referenced from:
          _main in Main.o
      &quot;Similarity::Similarity()&quot;, referenced from:
          _main in Main.o
      &quot;Similarity::~Similarity()&quot;, referenced from:
          _main in Main.o
    ld: symbol(s) not found for architecture x86_64
    collect2: ld returned 1 exit status
    make: *** [Aprog] Error 1

Thank you for reading through all that, any suggestions or solutions would be greatly appreciated.


Undefined Symbols for architecture x86_64: Compiling problems

I have the following:

    var text = &quot;&#220;bergro&#223;e &#196;pfel mit W&#252;rmern&quot;;

I&#39;m searching for a Javascript function to transform the text so that every special letter is represented by its HTML entity sequence like this:

    var newText = magicFunction(text);
    ...
    newText = &quot;&amp;Uuml;bergro&amp;szlig;e &amp;Auml;pfel mit W&amp;uuml;rmern&quot;;

The function should **not only** escape the letters of this example [but also all of these.][1]

How would you achieve that? Is there any existing function out there? (Plain, because a solution without a framework is preferred)


Btw: Yes, I&#39;ve seen [this question][2] but it doesn&#39;t address my need.


  [1]: http://www.w3.org/TR/html4/sgml/entities.html
  [2]: https://stackoverflow.com/questions/784586/convert-special-characters-to-html-in-javascript

How to convert characters to HTML entities using plain JavaScript

How can I set the degree symbol to a `TextView` in Android? 


Android set degree symbol to Textview

I&#39;m trying to figure out whether I can build a static library that hides all of its internal objects and functions, etc, except for the interfaces I want to export. I&#39;m experimenting with Xcode (gcc 4.2).

I&#39;ve used the `__attribute__((visibility(&quot;hidden&quot;)))` attribute on some C++ classes per [this documentation][1]. I&#39;ve also defined little helper C functions as being file-local (static), etc.

However, when I run `strings` on the resulting .a library file, even when compiled in Release configuration, I still see the names of my ostensibly-hidden classes, with their method names, and even the names of file-local functions strewn around in there as well. 

I&#39;ve added the `-fvisibility=hidden` and even `-fno-rtti` to the gcc flags. While this reduces some of the strings, the class names, method names, and static functions names are all still in there in plain or mangled-but-readable form. 

Is there a reliable way to get the compiler to build this stuff without having the string names of all the internal stuff emitted into the binary? It shouldn&#39;t be necessary to have for any external clients linking in.

(To clarify: I&#39;m asking about obfuscation of internal naming, versus literal export binding needs. I&#39;m disconcerted that all the internal workings are visible via the `strings` command, regardless of whether these symbols are formally exported or not.)

Thanks.

  [1]: http://developer.apple.com/mac/library/documentation/DeveloperTools/Conceptual/CppRuntimeEnv/Articles/SymbolVisibility.html

Symbol hiding in static libraries built with Xcode

While learning Ruby I&#39;ve come across the &quot;=&gt;&quot; operator on occasion. Usually I see it in the form of 

    :symbol =&gt; value

and it *seems* to be used frequently when passing values to functions. What exactly is that operator called? What does it do/mean? Is it built into Ruby or is it something that different frameworks like Rails and DataMapper add to the symbol class? Is it only used in conjunction with the symbol class? Thanks.

In Ruby what does &quot;=&gt;&quot; mean and how does it work?

I&#39;m trying to write my first unit tests for a calculator, but NetBeans says it can&#39;t find the symbol `assertEquals` and annotation `@Test`.  
Should i include something?  
I&#39;m using NetBeans 7.3.1 and W7.

    package calculator;
    
    import org.junit.Assert.*;
    
    public class UnitTests{
    
        @Test
        public void checkAdd(){
            assertEquals(2, Calculator.rpnCalc(&quot; 2 3 + &quot;));
        }
    }

EDIT: Thanks guys, importing it as static helped.
 Test annotation required only including

&gt;  import org.junit.Test;

Cannot find symbol assertEquals

I have used the following `ggplot` command:

	ggplot(survey, aes(x = age)) + stat_bin(aes(n = nrow(h3), y = ..count.. / n), binwidth = 10)
	  + scale_y_continuous(formatter = &quot;percent&quot;, breaks = c(0, 0.1, 0.2))
	  + facet_grid(hospital ~ .)
	  + theme(panel.background = theme_blank())

to produce

![alt text][1]

I&#39;d like to change the *facet* labels, however, to something shorter (like `Hosp 1`, `Hosp 2`...) because they are too long now and look cramped (increasing the height of the graph is not an option, it would take too much space in the document). I looked at the [facet_grid][2] help page but cannot figure out how.

  [1]: https://imgur.com/lXK7C.png
  [2]: https://ggplot2.tidyverse.org/reference/facet_grid.html

How to change facet labels?

When I say `{ :bla =&gt; 1, :bloop =&gt; 2 }`, what exactly does the `:` do? I read somewhere about how it&#39;s similar to a string, but somehow a symbol. 

I&#39;m not super-clear on the concept, could someone enlighten me?

What is the colon operator in Ruby?

Is there a corresponding X mark to &amp;#x2713; (`&amp;#x2713;`)? What is it?

In HTML I can make a checkmark with &amp;#x2713; . Is there a corresponding X-mark?

Unicode has a million icon-like glyphs, but they&#39;re very hard to search.

Is there a Unicode glyph that looks like a &quot;Binocular&quot; or &quot;magnifying glass&quot;?
Or is there a symbol that&#39;s used to mean &quot;Search&quot;, which is in Unicode?

Is there Unicode glyph Symbol to represent &quot;Search&quot;

I&#39;m rebuilding an old Java project in Javascript, and realized that there&#39;s no good way to do enums in JS.

The best I can come up with is: 

    const Colors = {
        RED: Symbol(&quot;red&quot;),
        BLUE: Symbol(&quot;blue&quot;),
        GREEN: Symbol(&quot;green&quot;)
    };
    Object.freeze(Colors);

The `const` keeps `Colors` from being reassigned, and freezing it prevents mutating the keys and values. I&#39;m using Symbols so that `Colors.RED` is not equal to `0`, or anything else besides itself.

**Is there a problem with this formulation? Is there a better way?**

*************************************************************************

*(I know this question is a bit of a repeat, but all the [previous Q/As](https://stackoverflow.com/q/287903/1048572) are quite old, and ES6 gives us some new capabilities.)*


----------


**EDIT:**

Another solution, which deals with the serialization problem, but I believe still has realm issues:

    const enumValue = (name) =&gt; Object.freeze({toString: () =&gt; name});

    const Colors = Object.freeze({
        RED: enumValue(&quot;Colors.RED&quot;),
        BLUE: enumValue(&quot;Colors.BLUE&quot;),
        GREEN: enumValue(&quot;Colors.GREEN&quot;)
    });

By using object references as the values, you get the same collision-avoidance as Symbols.

Enums in Javascript with ES6

I like this literal expression for an array of strings:

    %w( i can easily create arrays of words )

I am wondering if there is a literal to get an array of symbols. I know I can do 

    %w( it is less elegant to create arrays of symbols ).map( &amp;:to_sym )

but it would be so wonderful just to use a literal.

Is there a literal notation for an array of symbols?

A lot of times people use symbols as keys in a Ruby hash.

What&#39;s the advantage over using a string?

E.g.:

    hash[:name]

vs.

    hash[&#39;name&#39;]

Why use symbols as hash keys in Ruby?

I just stumbled across [this question][1] and I noticed the user is using some notation I&#39;ve never seen before:

&lt;!-- language: lang-css --&gt;

    @font-face {
       /* CSS HERE */
    }

So is this `@` symbol something new in CSS3, or something old that I&#39;ve somehow overlooked? Is this something like where with an ID you use `#`, and with a class you use `.`? Google didn&#39;t give me any good articles related to this. What is the purpose of the  `@` symbol in CSS?

  [1]: https://stackoverflow.com/questions/3451541/css-font-face-anti-aliasing

What is the purpose of the &#39;@&#39; symbol in CSS?

I have an sql column that is a string of 100 &#39;Y&#39; or &#39;N&#39; characters. For example: 

&gt; YYNYNYYNNNYYNY...

What is the easiest way to get the count of all &#39;Y&#39; symbols in each row.

How to count instances of character in SQL Column

How do I get an outline view in [sublime text editor][1] for Windows? 

The minimap is helpful but I miss a traditional outline (a klickable list of all the functions in my code in the order they appear for quick navigation and orientation)

Maybe there is a plugin, addon or similar? It would also be nice if you can shortly name which steps are neccesary to make it work.

There is a [duplicate of this question][2] on the sublime text forums.

[2]:http://www.sublimetext.com/forum/viewtopic.php?f=3&amp;t=993&amp;p=4308&amp;sid=1a162626960826ab21861f1203f64ec5#p4308


[1]:http://www.sublimetext.com/

How to get an outline view in sublime texteditor?

How do I list the symbols being exported from a .so file?  If possible, I&#39;d also like to know their source (e.g. if they are pulled in from a static library).

I&#39;m using gcc 4.0.2, if that makes a difference.

How do I list the symbols in a .so file

This symbol for the rupee, the currency of India, was approved by the Union Cabinet on 15 July 2010. How can I display it on a website?

![Indian currency symbol][1]
        



  [1]: http://i.stack.imgur.com/34A9t.png

Displaying the Indian currency symbol on a website

I&#39;m trying to find the Unicode symbol to make a button display the Unicode pause symbol. I was able to find that the Unicode play symbol is `&amp;#9658` but I&#39;m looking for the equivalent of the Unicode pause symbol.

HTML for the Pause symbol in audio and video control

I&#39;m reading about an algorithm (it&#39;s a path-finding algorithm based on A*), and it contains a mathematical symbol I&#39;m unfamiliar with: ∀

Here is the context:

&gt; v(s) ≥ g(s) = min&lt;sub&gt;s&#39;∈pred(s)&lt;/sub&gt;(v(s&#39;) + c(s&#39;, s)) ∀s ≠ s&lt;sub&gt;start&lt;/sub&gt;

Can someone explain the meaning of ∀?

Unfamiliar symbol in algorithm: what does ∀ mean?

If there are at least two instances of the same string in my script, should I instead use a symbol?

When to use symbols instead of strings in Ruby?

I&#39;d like to trace some code in GIMP and therefore need GIMP with debug symbols enabled. I don&#39;t remember whether I have enabled them during compilation. How to check that without recompiling the program?

How to check if program was compiled with debug symbols?

I wonder what is the difference between these two:

- `gcc -s`: Remove all symbol table and relocation information from the executable.

- `strip`:  Discard symbols from object files.

### Do they have the same meaning? 

### Which one do you use to: 

- reduce the size of executable? 
- speed up its running?

What is the difference between &quot;gcc -s&quot; and a &quot;strip&quot; command?

One of the most important rules and best practices when writing a library, is putting all symbols of the
library into a library specific namespace. C++ makes this easy, due to the `namespace` keyword. In
C the usual approach is to prefix the identifiers with some library specific prefix.

Rules of the C standard put some constraints on those (for safe compilation): A C compiler may look at only the first
8 characters of an identifier, so `foobar2k_eggs` and `foobar2k_spam` may be interpreted as the same
identifiers validly – however every modern compiler allows for arbitrary long identifiers, so in our times
(the 21st century) we should not have to bother about this.

But what if you&#39;re facing some libraries of which you cannot change the symbol names / idenfiers? Maybe you got
only a static binary and the headers or don&#39;t want to, or are not allowed to adjust and recompile yourself.


How to deal with symbol collisions between statically linked libraries?

How should I encode special characters into web pages? For instance I need this symbol ℃, which I used just by copying and pasting the character as I can see it now. This worked for the desktop browsers I checked with and also on iPad and iPhone but nothing is displayed on a Blackberry I used for testing. Is there a standard best practice for this? 

http://www.fileformat.info/info/unicode/char/2103/browsertest.htm

Best way to encode Degree Celsius symbol into web page?

Despite reading &quot;[Understanding Ruby Symbols][1]&quot;, I&#39;m still confused by the representation of the data in memory when it comes to using symbols.  If a symbol, two of them contained in different objects, exist in the same memory location, then how is it that they contain _different_ values?  I&#39;d have expected the same memory location to contain the same value.

This a quote from the link:

&gt; Unlike strings, symbols of the same name are initialized and exist in memory only once during a session of ruby

I don&#39;t understand how it manages to differentiate the values contained in the same memory location.

Consider this example:

    patient1 = { :ruby =&gt; &quot;red&quot; }
    patient2 = { :ruby =&gt; &quot;programming&quot; }

    patient1.each_key {|key| puts key.object_id.to_s}
    3918094
    patient2.each_key {|key| puts key.object_id.to_s}
    3918094

`patient1` and `patient2` are both hashes, that&#39;s fine.  `:ruby` however is a symbol.  If we were to output the following:

    patient1.each_key {|key| puts key.to_s}

Then what will be output? `&quot;red&quot;`, or `&quot;programming&quot;`?


Forgetting hashes for a second, I&#39;m thinking a symbol is a _pointer_ to a value.  The questions I have are:

* Can I assign a value to a symbol?
* Is a symbol just a pointer to a variable with a value in it?
* If symbols are global, does that mean a symbol always points to one thing?

  [1]: http://web.archive.org/web/20140314193235/http://glu.ttono.us/articles/2005/08/19/understanding-ruby-symbols


How to understand symbols in Ruby

I found these symbols in a function declaration several times, but I don&#39;t know what they mean.

**Example:**

    void raccogli_dati(double **&amp; V, double **p, int N) { 
      int ultimo = 3; 
      V = new double * [N/2]; 
      for(int i=0; i &lt; N/2; i++) { 
        V[i] = new double[N/2], std :: clog &lt;&lt; &quot;digita &quot; &lt;&lt; N/2 - i
                     &lt;&lt; &quot; valori per la parte superiore della matrice V: &quot;; 
        for(int j=i; j &lt; N/2; j++) 
          std :: cin &gt;&gt; V[i][j], p[ultimo++][0] = (V[i][j] /= sqrt(p[i][0]*p[j][0]));
      } 
      for(int i=1; i &lt; N/2; i++) 
        for(int j=0; j &lt; i; j++) 
           V[i][j] = V[j][i];
    }


Meaning of *&amp; and **&amp; in C++

Is there a Python equivalent to Ruby symbols? 

 - If so then what is it?

 - If not then are we stuck with using **strings** as our **keys** in dictionaries only?

Is there a Python equivalent to Ruby symbols?

How can I convert a symbol type into a string in Emacs lisp? 

I wasn&#39;t able to find a `symbol-to-string` function or anything similar.

Convert Symbol to a String in Elisp

&gt;**UPDATE**: Recently a [brilliant article from Mozilla][2] came up. Read it if you&#39;re curious.

As you may know they are [planning to include][1] new Symbol primitive type in ECMAScript 6 (not to mention some other crazy stuff). I always thought that the `:symbol` notion in Ruby is needless; we could easily use plain strings instead, like we do in JavaScript. And now they decide to complicate things in JS with that. 

I don&#39;t understand the motivation. Could someone explain to me whether we really need symbols in JavaScript?

  [1]: https://people.mozilla.org/~jorendorff/es6-draft.html#sec-ecmascript-language-types-symbol-type

  [2]: https://hacks.mozilla.org/2015/06/es6-in-depth-symbols/

What is the motivation for bringing Symbols to ES6?

How can you remove letters, symbols such as `∞&#167;&#182;•&#170;&#186;&#186;&#171;≥≤&#247;` but leaving plain numbers 0-9, I want to be able to not allow letters or certain symbols in an input field but to leave numbers only.

[Demo][1].

If you put any symbols like `&#161; € # &#162; ∞ &#167; &#182; • &#170;` or else, it still does not remove it from the input field. How do you remove symbols too? The `\w` modifier does not work either.


  [1]: http://jsfiddle.net/4vuHN/

Regex to remove letters, symbols except numbers

What&#39;s the difference between a string and a symbol in Ruby and when should I use one over the other?

What&#39;s the difference between a string and a symbol in Ruby?

I know what it means in a comment for documentation purposes, but outside of that what does it mean? (I would normally just google this but every non letter symbol shows up in results)

in java what does the @ symbol mean?

&gt; **Possible Duplicate:**  
&gt; [What are some example use cases for symbol literals in Scala?](https://stackoverflow.com/questions/780287/what-are-some-example-use-cases-for-symbol-literals-in-scala)  

&lt;!-- End of automatically inserted text --&gt;

What&#39;s the purpose of Symbol and why does it deserve some special *literal* syntax e. g. `&#39;FooSymbol`?

Purpose of Scala&#39;s Symbol?

I have a problem. I have found the HTML code for the downwards arrow, `&amp;darr;` (&amp;darr;)

Cool. Now I need to use it in CSS like so:

    nav a:hover {content:&quot;&amp;darr&quot;;}

That obviously won&#39;t work since `&amp;darr;` is an HTML symbol. There seems to be less info about these &quot;escaped unicode&quot; symbols that are used in css. There are other symbols like `\2020` that I found but no arrows. What are the arrow codes?


Placing Unicode character in CSS content value

What is the function of symbol in ruby? what&#39;s difference between string and symbol?
Why is it not a good idea to dynamically create a lot of symbols? 

Why is it not a good idea to dynamically create a lot of symbols in ruby (for versions before 2.2)?

I am loading a YAML file in Rails 3.0.9 like this:

    APP_CONFIG = YAML.load(File.read(File.expand_path(&#39;../app.yml&#39;, __FILE__)))

It loads the all of the contents like hierarchical hashes, no problem.  The part I don&#39;t like is the fact that the hashes can only be accessed with single or double quotes but not a symbol.  

    APP_CONFIG[&#39;mailer&#39;][&#39;username&#39;]  # works fine
    APP_CONFIG[:mailer][:username]    # doesn&#39;t

Any thoughts?

Rails load YAML to hash and reference by symbol

Is there a tool for reading Mac OS X binaries that would print information about relocation tables and symbol offsets similar to this `readelf` output?

    readelf -r app
    
    Relocation section &#39;.rel.dyn&#39; at offset 0x5ec contains 2 entries:
     Offset     Info    Type            Sym.Value  Sym. Name
    08049d58  00001706 R_386_GLOB_DAT    00000000   __gmon_start__
    08049d60  00000305 R_386_COPY        08049d60   _ZSt4cout
    
    Relocation section &#39;.rel.plt&#39; at offset 0x5fc contains 13 entries:
     Offset     Info    Type            Sym.Value  Sym. Name
    08049d24  00000107 R_386_JUMP_SLOT   0804868c   print
    08049d28  00000207 R_386_JUMP_SLOT   0804869c   _ZNSt8ios_base4InitC1E
    08049d2c  00000507 R_386_JUMP_SLOT   080486ac   _ZStlsISt11char_traits
    08049d30  00000607 R_386_JUMP_SLOT   080486bc   _ZNSolsEPFRSoS_E
    08049d34  00000707 R_386_JUMP_SLOT   08048664   _init
    08049d38  00000807 R_386_JUMP_SLOT   080486dc   sleep
    08049d3c  00000907 R_386_JUMP_SLOT   080486ec   _ZNKSsixEj
    08049d40  00000b07 R_386_JUMP_SLOT   080486fc   _ZNKSs4sizeEv
    08049d44  00000c07 R_386_JUMP_SLOT   0804870c   __libc_start_main
    08049d48  00000d07 R_386_JUMP_SLOT   08048ae4   _fini
    08049d4c  00001307 R_386_JUMP_SLOT   0804872c   _ZSt4endlIcSt11char_tr
    08049d50  00001507 R_386_JUMP_SLOT   0804873c   __gxx_personality_v0
    08049d54  00001607 R_386_JUMP_SLOT   0804874c   _ZNSt8ios_base4InitD1E

In this example, `print` is a function loaded from a shared library (I wrote) at runtime.  `readelf` is able to display information about its location inside the `app` binary.

readelf-like tool for Mac OS X?

I am compiling an IPhone application via command line (so no XCode options involved) and I am unable to get my symbol names to show when profiling with Instruments. I have tried several flags such as -gdawrf-2 and -g without any success. I have also tried using dsymutils to generate a .dSYM file but i have no clue how I&#39;m supposed to use it so that failed aswell.

Any help will be greatly appreciated!

Missing symbol names when profiling IPhone application with Instruments

What does `::=` mean in programming documentation?
&lt;br /&gt;For example in the [Lua documentation][1]: or in [Python documentation][2].


  [1]: http://www.lua.org/manual/5.2/manual.html#3.2
  [2]: http://docs.python.org/release/2.7.1/reference/lexical_analysis.html#identifiers

What does a double colon followed by an equals sign (::=) mean in programming documentation?

Scala has symbols - names that start with a single quote &#39; and which are a kind of string constants.

I know symbols from Ruby (where they start with a colon). In Ruby they are used for some meta-programming tasks, like generating getters and setters for member variables (for example `attr_reader :name` to generate a getter for `name`).

I haven&#39;t seen a lot of use of symbols in Scala code yet. What are practical uses for symbols in Scala?

Practical examples of using symbols in Scala?

During a refactor of an iOS project, I ran into this bear of a bug. During the linking phase, I get this message:

&gt;ld: duplicate symbol _OBJC_IVAR_$_TinCanViewController.currentViewController in /path/to/TinCanViewController-E98A666B7AF2673A.o and /path/to/TinCanViewController-E98A666B7AF2673A.o

As far as I can tell, it looks like it claims `TinCanViewController-E98A666B7AF2673A.o` is declaring the specified symbol twice; both paths are pointing to the exact same .o file. I ran `nm` on that specific file, and it only included that symbol once: 

&gt; 00008150 S _OBJC_IVAR_$_TinCanViewController.currentViewController

I ran `nm` on all the other .o files in the directory to see if they were somehow declaring this symbol, too, but they&#39;re not. This happens to any member I add to the TinCanViewController class - it&#39;s not specific to currentViewController.

I feel like I must be somehow linking against the class twice somehow, but I&#39;ve pretty assiduously gone through and checked all references to this class. In the refactored version, there are basically none. The AppDelegate includes it, but right now it&#39;s basically just a passthrough class that loads another ViewController at the start. No other classes in the project include it.

Any suggestions on what might be causing this or how I might debug it better?


Duplicate symbol issues

Can someone please explain to me what the **`#`** symbol means in MS SQL Code.

I&#39;ve tried Googling it, and even searching on StackOverflow, but can&#39;t seem to find the answer.

I feel like an idiot - having one of &quot;those&quot; days. Please help.

What does the SQL # symbol mean and how is it used?

What does the `to_sym` method do? What is it used for?


What does the Ruby method &#39;to_sym&#39; do?

Does there exist a Unicode symbol that represents a person? I would expect something like this:

[![pictogram of a stick figure][1]][1]

I need a short way to represent a *price per person*, such as “25€/person”, but with the word “person” replaced with a Unicode character for a person. The benefit will be that the picture isn’t tied to the English language.

  [1]: http://i.stack.imgur.com/tDjcv.png

What Unicode symbol represents a person?

Could someone explain the columns shown of the symbol table using `readelf`?

What are the meanings of the columns of the symbol table displayed by readelf?

I am learning rails and following [this thread](https://stackoverflow.com/questions/1961030). I am stuck with the `to_proc` method. I consider symbols only as alternatives to strings (they are like strings but cheaper in terms of memory). If there is anything else I am missing for symbols, then please tell me. Please explain in simple way what `to_proc` means and what it is used for.

All Symbols Solutions on Gang of Coders

Total of 49 Symbols Solutions