ELI (programming language)

ELI[3] is an interactive array programming language system based on the 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 #include in 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.

ELI[1]
Paradigmarray
Designed byWai-Mee Ching
DeveloperHanfeng Chen[2] (Rapidsoft)
First appeared2011; 13 years ago (2011)
Stable release
0.3 / August 10, 2015; 9 years ago (2015-08-10)
Typing disciplinedynamic
Implementation languageC++, Qt
PlatformIA-32, x86-64
OSCross-platform: Windows, Linux, macOS
LicenseFreeware
Filename extensions.esf .eli
Websitefastarray.appspot.com
Influenced by
APL, Q

By replacing each APL character with one or two ASCII characters, ELI retains APL's succinct and expressive way of array programming compared with MATLAB or 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

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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.

Version 0.3 adds several new features.[4]

  • Like: string match
  • Match
  • []PP: printing precision control
  • )time: performance measure
  • []: standard input
  • Date and time attributes
  • File handle: []open, []close, []write, and []get
  • Semicolon (;)

Example code

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A line of ELI executes from right to left as a chain of operations; anything to the right of ‘//’ is a comment.

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

      !10
1 2 3 4 5 6 7 8 9 10

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

      5 * 2 + 10 // from right to left, 5 * (2 + 10)
60

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

      {add: x+y} // short function form
add
      1 add 2    // 1+2
3
      1 add !10  // 1+(1..10)
2 3 4 5 6 7 8 9 10 11

The $ rotation operator returns the reverse order of a vector.

      $!10       // reverse
10 9 8 7 6 5 4 3 2 1

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

      2 3#!6     // 2 dimension array (matrix)
1 2 3
4 5 6

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

      x <- !20   // 1..20
      x
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20
      (1 = 2|x) / x  // get odd numbers from x
1 3 5 7 9 11 13 15 17 19

File extensions

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Two file extensions are used in ELI for exchanging and sharing code for different purposes: .esf and .eli.

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

      )out MyScript
      )lib
MyScript.esf
      )fload MyScript
saved 2017.02.17 10:23:55 (gmt-5)

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

      )save MyWorkspace
      )load MyWorkspace
saved 2017.02.17 10:57:19 (gmt-5)

References

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  1. ^ ELI: a simple system for array programming
  2. ^ ELI - mirror site in the Sable lab at McGill University
  3. ^ "ELI: A System for Programming with Arrays". Disqus.
  4. ^ Chen, Hanfeng (2015). "Overview". ELI, a System for Programming with Arrays. Fastarray.appspot.com. Retrieved 26 February 2018.
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