ELI (programming language): Difference between revisions

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{{Infobox programming language

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'''ELI'''<ref name="website">[{{cite web |url=https://fastarray.appspot.com/ |title=ELI: -A officialSystem site]for HostedProgramming onwith GoogleArrays App Engine|website=Disqus}}</ref> is an interactive [[array programming]] language system based on the [[programming language]] [[APL (programming language)|APL]]. It has most of the functions of the [[International Organization for Standardization]] (ISO) APL standard ''ISO/IEC 13751:2001'', and also list for non-homogeneous or non-rectangular data, complex numbers, symbols, temporal data, and control structures. A scripting file facility is available to organize programs in a fashion similar to using <code>#include</code> in [[C (programming language)|C]], which also provides convenient data [[input/output]]. ELI has dictionaries, tables, and a basic set of [[SQL]]-like statements. For performance, it has a [[compiler]] restricted to flat array programs.

By replacing each [[APL syntax and symbols|APL character]] with one or two [[ASCII]] characters, ELI retains APL's succinct and expressive way of array programming compared with [[MATLAB]] or [[Python (programming language)|Python]], ELI encourages a [[dataflow programming]] style, where the output of one operation feeds the input of another.

ELI is available without charge, as [[freeware]], on [[Windows]], [[Linux]], and [[macOS]].

==Version 0.3==

ELI version 0.3, described as a stable release, was released on August 10, 2015. It integrates with a cross-platform IDE, ELI Studio, which provides a code editor with specialized functions to write and load ELI code. Three added widgets are used to monitor functions, variables, libraries and command history.

==New features==

Version 0.3 adds several new features.<ref>{{cite web |url=https://fastarray.appspot.com/releasenote/Eli-v0.3.html |title=Overview |last=Chen |first=Hanfeng |date=2015 |website=ELI, a System for Programming with Arrays |publisher=Fastarray.appspot.com |access-date=26 February 2018}}</ref>

* Like: string match

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* File handle: []open, []close, []write, and []get

* Semicolon (;)

Documentation:

* [https://fastarray.appspot.com/docs/ Online documentation]

* [https://www.youtube.com/channel/UCpq4XRc7A1YNbEnBRx9-jzw YouTube channel]

==Example code==

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Exclamation point (!) is an interval function. It can generate a vector of n integer from 1 to n.

<sourcesyntaxhighlight lang="text">

!10

1 2 3 4 5 6 7 8 9 10

</syntaxhighlight>

</source>

The execution order of ELI is from right to left, and all primitive functions have equal precedence.

<sourcesyntaxhighlight lang="textq">

5 * 2 + 10 // from right to left, 5 * (2 + 10)

60

</syntaxhighlight>

</source>

In the next example a function <code>add</code> is declared in a short function form. The arguments of the function can be either a scalar or a vector.

<sourcesyntaxhighlight lang="textq">

{add: x+y} // short function form

add

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1 add !10 // 1+(1..10)

2 3 4 5 6 7 8 9 10 11

</syntaxhighlight>

</source>

The <code>$</code> rotation operator returns the reverse order of a vector.

<sourcesyntaxhighlight lang="textq">

$!10 // reverse

10 9 8 7 6 5 4 3 2 1

</syntaxhighlight>

</source>

A 2-by-3 matrix (or higher dimension array, e.g., <code>2 3 4#!24</code>) can be generated by <code>#</code> with left argument <code>2 3</code>.

<sourcesyntaxhighlight lang="textq">

2 3#!6 // 2 dimension array (matrix)

1 2 3

4 5 6

</syntaxhighlight>

</source>

In first line below the <code>x</code> is assigned with a vector from 1 to 20. Then, <code>1 = 2|x</code> returns odd number <code>True</code> and even number <code>False</code>. The <code>/</code> is a primitive function for compression which '''picks up''' the value in <code>x</code> corresponding to the <code>True</code> values in its left argument.

<sourcesyntaxhighlight lang="textq">

x <- !20 // 1..20

x

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(1 = 2|x) / x // get odd numbers from x

1 3 5 7 9 11 13 15 17 19

</syntaxhighlight>

</source>

==File extensions==

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An ELI file with extension <code>.esf</code> is a script file which contains all methods and data. A simple way to create a script file is using the command <code>)out</code>. However, a clean workspace with no debugging or error information left is needed before a script file can be created. Later the command <code>)fload</code> can be used to reload the script file.

<sourcesyntaxhighlight lang="text">

)out MyScript

)lib

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)fload MyScript

saved 2017.02.17 10:23:55 (gmt-5)

</syntaxhighlight>

</source>

An ELI file with extension <code>.eli</code> is an ELI workspace file which contains everything in a workspace. <code>save</code> and <code>load</code> are commands for workspace files.

<sourcesyntaxhighlight lang="textq">

)save MyWorkspace

)load MyWorkspace

saved 2017.02.17 10:57:19 (gmt-5)

</syntaxhighlight>

</source>

==Development notes==

* (Dec. 2016) ELI began to actively maintain its online language reference manual which can be found at [https://fastarray.appspot.com/docs/EliReference.html fastarray/docs]

* (Dec. 2016) An ELI primer was released

==See also==

* [[Q (programming language from Kx Systems)|Q]], programming language from Kx Systems

==References==

{{Reflist}}

==External links==

* {{Official website|fastarray.appspot.com}}

* [https://fastarray.appspot.com/docs/ Online documentation]{{Dead link|date=December 2019 |bot=InternetArchiveBot |fix-attempted=yes}}

* [https://www.youtube.com/channel/UCpq4XRc7A1YNbEnBRx9-jzw YouTube channel]

{{APL programming language}}