Edit - Code Golf Stack Exchange

You are not logged in. Your edit will be placed in a queue until it is peer reviewed.

We welcome edits that make the post easier to understand and more valuable for readers. Because community members review edits, please try to make the post substantially better than how you found it, for example, by fixing grammar or adding additional resources and hyperlinks.

Required fields*

Rev

Required fields*

Showcase of Languages

Notes

This thread is open and unlocked only because the community decided to make an exception. Please do not use this question as evidence that you can ask similar questions here. Please do not create additional showcase questions.

This is no longer a popularity-contest, nor are snippet lengths limited by the vote tally. If you know this thread from before, please make sure you familiarize yourself with the changes.

This thread is dedicated to showing off interesting, useful, obscure, and/or unique features your favorite programming languages have to offer. This is neither a challenge nor a competition, but a collaboration effort to showcase as many programming languages as possible as well as possible.

How this works

All answers should include the name of the programming language at the top of the post, prefixed by a #.
Answers may contain one (and only one) factoid, i.e., a couple of sentences without code that describe the language.
Aside from the factoid, answers should consist of snippets of code, which can (but don't have to be) programs or functions.
The snippets do not need to be related. In fact, snippets that are too related may be redundant.
Since this is not a contest, all programming languages are welcome, whenever they were created.
Answers that contain more than a handful of code snippets should use a Stack Snippet to collapse everything except the factoid and one of the snippets.
Whenever possible, there should be only one answer per programming language. This is a community wiki, so feel free to add snippets to any answer, even if you haven't created it yourself. There is a Stack Snippet for compressing posts, which should mitigate the effect of the 30,000 character limit.

Answers that predate these guidelines should be edited. Please help updating them as needed.

Current answers, sorted alphabetically by language name

$.ajax({type:"GET",url:"https://api.stackexchange.com/2.2/questions/44680/answers?site=codegolf&filter=withbody",success:function(data){for(var i=0;i<data.items.length;i++){var temp=document.createElement('p');temp.innerHTML = data.items[i].body.split("\n")[0];$('#list').append('<li><a href="/a/' + data.items[i].answer_id + '">' + temp.innerText || temp.textContent + '</a>');}}})

<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script><base href="http://codegolf.stackexchange.com"><ul id="list"></ul>

Answer*

# [Factor](http://factorcode.org)

**Factor** is a concatenative, stack-oriented and object-functional programming language first developed by Slava Pestov in 2003 as a *scripting* language for a game engine. Factor unites the simplicity and durability of Forth's stack-procedural paradigm and extensible word-based syntax, with the applicative, point-free and functional styles of Joy and Lisp.

In Factor, whitespace is the `apply` operator, the default operation. All words are first class objects; in fact, almost everything is a first-class object which means tons of possibility for extensible syntax, new types and literals, and all the other awesomeness introduced by [Homoiconicity](http://en.wikipedia.org/wiki/Homoiconicity).

Unlike Forth, Factor prefers to use the many, many different higher-order words at its disposal over shuffle words, which should be avoided for the sake of readability and idiomaticity.

You can [download a Factor binary](http://factorcode.org), or [find Factor in active development on GitHub](http://github.com/factor/factor).

Oh, its [documentation](http://docs.factorcode.org) is amazing, and the Listener UI / IDE (written in pure Factor) has the documentation offline and searchable. :D

I mentioned above that Factor was a scripting language -- that was back when it ran on the JVM, too. Factor, its runtime and its optimising native-code compiler are 97% pure Factor, with just 3% being low-level C++ for the VM and bootstrap.

I guess we'll go top-to-bottom, Iunno.

[Link to this answer](https://codegolf.stackexchange.com/a/76437/46231), [Link to Edit](https://codegolf.stackexchange.com/posts/76437/edit).

### Length 1

For length 1, let's start at the most basic building block of Factor: the word that lets us make more words.

[Factor's pretty verbose](https://codegolf.stackexchange.com/questions/75610) so there's not much to do with one byte, because the "words" are literally *words*, and there's a lot of whitespace everywhere.

This means the fun in golfing comes not from shortening identifiers, but from re-**Factor**ing, which is where Factor gets its name. :D

Factor gets a lot of its pleasant syntax from Forth. The simplest flavour of [word-definition word, `:`](http://docs.factorcode.org/content/word-__colon__,syntax.html) is an example.

Use it like:

: word-name ( input -- output ) word-body ;

The word will then be callable by `word-name`, and `word-body` will execute, taking and putting things to and from the stack. `word-name`'s stack effect *must* match its actual effect on the stack. If `add` takes two numbers from the stack and adds them together, leaving the result on the stack,

: add ( a b -- x ) + ;

Then its stack effect is that of the only word in its body (part of the power of concatenative languages). The identifiers in the effect don't matter, just that they are a proper representation.

### Length 2

Another word-definition word, [`::`](http://docs.factorcode.org/content/word-__colon____colon__,locals.html), allows the use of the [`:>`](http://docs.factorcode.org/content/word-__colon____gt__,locals.html) lexical-variable-binding word, and causes inputs to be bound to the names in the stack effect.

:: join-strings ( a b -- x ) a b suffix! ;

To bind a value to a name:

:: var-demo ( a b c -- ) a c + b * sqrt :> val ;

`val` goes out of scope when the word is done executing.

### Length 3

[ ]

Here, I'll let you have a guess at what this is. Hint: It's not an array.

---
You don't know? 
It's a [quotation](http://docs.factorcode.org/content/word-[,syntax.html) -- it allows putting an executable block of literal code on the stack, that the higher-order functional and applicative words can manipulate.

Brackets for blocks come from Smalltalk syntax (with the `locals` vocabulary you also get `[| param | code ]` which kind of resembles Smalltalk's `[ :param | code ]`).

### Length 4

I'll try to do something more interesting this time, as fede s. suggested in the comments:

2bi@

Before I explain what this is, I should probably first explain something about Factor identifiers.

A valid Factor identifier is any string which matches the following:

^[^"][^\s]+$

Yes, that's it. Any identifier can contain any character that isn't whitespace, and it can't begin with one or more `"`s, because strings are special to the lexer. It can have `"` elsewhere within it, though.

The NUL byte, the character at UTF8 888 and the byte at 127, ASCII DEL are all valid identifiers. For portability, sometimes `SYMBOL`s may be stripped of their non-ASCII bytes (Windows, for instance).

This may be rather shocking to the C people and the Python people (and even the Lisp people, who allow some nice stuff in names), but fear not, for you will come to like it.

So `2bi@` is just one identifier, one name for one function. But what does it do? Well, the [`bi@`](http://docs.factorcode.org/content/word-bi,kernel.html) function applies one quotation to two items on the stack:

"5" "10" [ string>number ] bi@
 
 --- Data stack:
 5 
 10

(bi stands for [bifurcate](http://google.com/search?q=define:bifurcate), if you were curious.)

"5" "10" "15" "20" [ append string>number ] 2bi@

--- Data stack:
 510
 1520

[`2bi@`](http://docs.factorcode.org/content/word-2bi__at__,kernel.html), like `2map`, takes a quotation with stack effect `( obj1 obj2 -- ... )`, which gets applied first to `w` and `x`, then `y` and `z` in pairs.

### Length 5

Finally, a word for working with sequences. Factor is no APL / J / K / Octave / what have you, but its array processing skills are... close... kinda.

union

If you're familar with Python (like I am), then you may recognise this better as the `|` operator on `set`s:

{ 1 2 3 } { 2 3 4 } union

--- Data stack:
 { 1 2 3 4 }

Removes duplicates while performing element-wise OR. Technically, the [`union`](http://docs.factorcode.org/content/word-union,sets.html) word is from the [`sets`](http://docs.factorcode.org/content/article-sets.html) vocabulary and not the `sequences` vocab. This is because, like Python, sets are special, super-fast immutable sequences that don't allow duplicate entries.

Also much like Python, any sequence (byte vector, hashtable, set, etc) that implements the [Sequence protocol](http://docs.factorcode.org/content/article-sequence-protocol.html) (`__iter__` being the equivalent in Python) is considered fair game and supports a well-defined set (hah) of operations, so any word that works on a generic sequence A will also work on a generic set B if both have the right method dispatch.

### Length 6

Ooh, more arrays! (Note that arrays are immutable; all operations on them yield new arrays and the old ones are GC'd. Vectors are mutable and slower, but we'll cross that bridge when we get there.)

2array

This is a *highly* useful word. Any guess at what it does? Here:

IN: scratchpad 1 2 2array

--- Data stack:
 { 1 2 }

IN: scratchpad { 3 4 } 2array

--- Data stack:
 { { 1 2 } { 3 4 } }

Well shucks, it takes **two** things off the stack and makes a new array from them. `1array`, `3array` and `4array` all do *exactly* what you'd expect, and `narray` takes an arbitrary `n` argument, to avoid messy concatenation code.

If I may digress yet again about naming...

In Java or Python, one might call this function `values2array` or `valuesToArray` or even `values2Array`. However, here in Factor-land, we have some [conventions](http://docs.factorcode.org/content/article-conventions.html).

Remember my spiel about identifiers? Numeric digits in names should only be used for indicating real numbers or counts of things; in particular, this means `2array` should not be read as `to-array` but as `two-array`.

The word which does `to-array` is called `>array`. The word which turns a number to a string is `number>string`, and the word which turns an object's slots to an array is `tuple>array`. See a pattern? Hmm.

Users of [Racket](http://racket-lang.org) will feel right at home with these sorts of names, since Racket uses stuff like `number->string`.

If this is an answer to a challenge…

…Be sure to follow the challenge specification. However, please refrain from exploiting obvious loopholes. Answers abusing any of the standard loopholes are considered invalid. If you think a specification is unclear or underspecified, comment on the question instead.
…Try to optimize your score. For instance, answers to code-golf challenges should attempt to be as short as possible. You can always include a readable version of the code in addition to the competitive one. Explanations of your answer make it more interesting to read and are very much encouraged.
…Include a short header which indicates the language(s) of your code and its score, as defined by the challenge.

More generally…

…Please make sure to answer the question and provide sufficient detail.
…Avoid asking for help, clarification or responding to other answers (use comments instead).

Draft saved

Draft discarded

Edit Summary*

Cancel

\$\begingroup\$ @fedes. Done! Have a suggestion for #5? You can even edit it in yourself; I'll make sure to accept it :P \$\endgroup\$

cat
– cat

2016年04月27日 22:36:44 +00:00
Commented Apr 27, 2016 at 22:36
1

\$\begingroup\$ On the naming conventions and Racket (actually from scheme), there's also - for separating words (map-index), ! for mutators (union!) and ? for predicates and tests (odd?)! Good choice IMHO :D \$\endgroup\$

fede s.
– fede s.

2016年04月28日 02:29:07 +00:00
Commented Apr 28, 2016 at 2:29
2

\$\begingroup\$ Why did someone just downvote this?? \$\endgroup\$

cat
– cat

2016年04月28日 17:11:36 +00:00
Commented Apr 28, 2016 at 17:11
4

\$\begingroup\$ Also WTF w/downvote? Someone pushing another language higher? ಠ~ಠ \$\endgroup\$

fede s.
– fede s.

2016年05月01日 04:24:32 +00:00
Commented May 1, 2016 at 4:24
1

\$\begingroup\$ You owe us a few more snippets! \$\endgroup\$

jqkul
– jqkul

2016年06月27日 00:11:32 +00:00
Commented Jun 27, 2016 at 0:11

| Show 12 more comments

How to Edit

Correct minor typos or mistakes
Clarify meaning without changing it
Add related resources or links
Always respect the author’s intent
Don’t use edits to reply to the author

How to Format

create code fences with backticks ` or tildes ~
```
like so
```
add language identifier to highlight code
```python
def function(foo):
print(foo)
```
put returns between paragraphs
for linebreak add 2 spaces at end
_italic_ or **bold**
indent code by 4 spaces
backtick escapes `like _so_`
quote by placing > at start of line
to make links (use https whenever possible)

<https://example.com>

[example](https://example.com)

<a href="https://example.com">example</a>
MathJax equations \$\sin^2 \theta\$

formatting help »
answering help »

MathJax help »

How to Tag

A tag is a keyword or label that categorizes your question with other, similar questions. Choose one or more (up to 5) tags that will help answerers to find and interpret your question.

complete the sentence: my question is about...
use tags that describe things or concepts that are essential, not incidental to your question
favor using existing popular tags
read the descriptions that appear below the tag

If your question is primarily about a topic for which you can't find a tag:

combine multiple words into single-words with hyphens (e.g. code-golf), up to a maximum of 35 characters
creating new tags is a privilege; if you can't yet create a tag you need, then post this question without it, then ask the community to create it for you

popular tags »