NIAL

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NIAL

• Nested Interactive Array Language
• Dennis Brown
• Northern Kentucky University
• CSC 507 November 2005

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Origins of NIAL

• Based on nested array theory developed by Dr.
  Trenchard More, Jr.
• Invented in 1981 by Michael Jenkins of Queens
  University in Kingston, Ontario
• Influenced by APL and Lisp
• NIAL is an acronym for Nested Interactive Array
  Language, but is also a reference to Njals Saga
  (a Nordic legend)

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APL vs. NIAL

• APL was invented in 1962
• Very efficient for some types of calculation, but
  required a special character set

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APL vs. NIAL (cont.)

• NIAL uses keywords instead of symbols, so no
  custom keyboard is required
• For example, ? (rho) in APL becomes reshape in
  NIAL
• NIAL also adds control structures (from
  imperative languages) that APL did not have
• The original version of APL did not support
  nested arrays

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NIAL Data Types

• Numbers
• integers
• floating points
• booleans (l, o, True, False)
• Characters
• X, v, 3
• Lists
• 3 C 5 (strand notation)
• 3 C 5
• (empty list)

• Strings
• abc
• a b c
• Phrases
• dog
• phrase dog
• Faults
• ?conform

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Strings vs. Phrases

• A string is a list
• first abc ? a last abc ? c
• A phrase is atomic
• first abc ? abc last abc ? abc

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Lists Examples

• sum 2 3 4
• 9
• sum 2 3 4
• 2 3 4
• sum (2 3 4) (1 2 3)
• 3 5 7
• each sum (2 3 4) (1 2 3)
• 9 6

• x y z 5 6 7
• assigns 5 to x, 6 to y, 7 to z
• 1 2 3 2
• 2 4 6
• 1 2 3 3 2 1
• 3 4 3
• 1 2 3 3 2 1
• 3 6 9 2 4 6 1 2 3

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Lisp vs. NIAL

• (car 1 2 3)
• 1
• (cdr 1 2 3)
• (2 3)
• (cons 1 (2 3))
• (1 2 3)

• first 1 2 3
• 1
• rest 1 2 3
• 2 3
• hitch 1 (2 3)
• 1 2 3

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Tables

• A table is a multi-dimensional list
• The reshape function can be used to create a
  table with a specified number of rows and columns
• 2 3 reshape 1 2 3 4 5 6 7 8
• 1 2 3
• 4 5 6
• 2 3 reshape 1 2 3 4
• 1 2 3
• 4 1 2

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Tables Continued

• x 3 3 reshape count 9
• 1 2 3
• 4 5 6
• 7 8 9
• x 2, (row slice)
• 7 8 9
• x ,2 (col. slice)
• 3 6 9
• x _at_ (1 2)
• 6

• post 1 2 3
• 1
• 2
• 3

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Functions

• Functions are defined using the syntax is
  operation, followed by the formal parameters,
  and then the function body enclosed in braces
• Functions are evaluated using right associativity
• Examples
• factorial IS OPERATION x count x
• nthroot IS OPERATION x n power x ( reciprocal n
  )

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Transformers

• A transformer changes how functions are applied
• each is a built-in transformer that applies a
  function to each value of a list
• each first (abc def) (3 7 8) (z x q)
• abc 3 z
• New transformers can be created using IS
  TRANSFORMER
• Transformers were a novel feature in NIAL, and
  allow the language to support parallel
  architectures efficiently

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Atlases

• An atlas is a list of functions that can be
  applied to a data item, producing a list of
  results
• first, last, reverse a b c
• a c cba brackets are used because cba is
  a list!
• , -, , /, quotient 12 7
• 19 5 84 1.71 1

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Different Ways of Saying the Same Thing

• x aeiou
• x True
• x 3 4
• x 3 4
• x gets 3 4 5
• x _at_ (0 3)
• x _at_ (0 3)

• x a e i o u
• x l
• x gets 3 plus 4
• x gets plus 3 4
• x 3 times prod 4 5
• 0 3 choose x
• x 0, 3

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IF Statements

• IF, ELSE, ELSEIF, and ENDIF are supported
• Comparison operators and boolean operations are
  available
• IF (x gt 3.4) and (y lt 7) THEN
• out_of_range True
• ELSE
• out_of_range False
• ENDIF

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CASE Statements

• CASE statements allow selection based on a value
  (not necessarily an integer)
• An optional ELSE clause handles the default case
• Each non-default case must end with END there
  is no fall-through like in C and Java
• CASE n FROM
• 1 value one END
• 2 value two END
• ELSE value unknown
• ENDCASE

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Loops

• NIAL supports the three usual types of loops
• WHILE condition DO expressions ENDWHILE
• REPEAT expressions UNTIL condition ENDREPEAT
• FOR variable WITH range DO expressions
  ENDFOR
• The count function is useful with FOR loops
• FOR i WITH count 10 DO write(i) ENDFOR
• It is better to use the EACH transformer, however
• The EXIT statement can be used to force a loop to
  terminate

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QNial Interpreter

• QNial allows NIAL statements to be entered and
  interpreted dynamically
• Windows version is now available free from NIAL
  Systems (www.nial.com)
• C source code for QNial is also available free
  of charge

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QNial in Action
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The Future of NIAL

• NIAL has been used in academic research
  (particularly in AI) and at some insurance
  companies, but has declined in popularity since
  the 1980s
• Newer languages in its niche can do the same
  tasks just as well or better
• APL version 2
• J and its successors
• J is available for free NIAL was very expensive
  until recently
• NIAL is not easy to integrate with native C
  libraries
• Best use of NIAL is as a prototyping language

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References

• Nial Systems Limited
• http//www.nial.com
• Qnial Research Project
• http//www.qnial.net
• A Quick Look at Nial, Journal of J/APL
• http//www.apl.demon.co.uk/aplandj/qnial.html
• Comparison of array languages, Keith Smillie
• http//www.cs.ualberta.ca/smillie/ComputerAndMe/P
  art23.html
• APL programming language, Wikipedia
• http//en.wikipedia.org/wiki/APL_programming_langu
  age

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Questions?