Ella (Programming Language)

ELLA
Developer(s)	Royal Signals and Radar Establishment
Initial release	1986; 37 years ago
Written in	ALGOL 68RS
Operating system	VMS
Platform	ICL 2900 Series, Multics, VAX
Available in	English
Type	Hardware description language
License	public domain (parts)

ELLA is a hardware description language and support toolset, developed in the United Kingdom by the Royal Signals and Radar Establishment (RSRE) during the 1980s and 1990s, which also developed the compiler for the programming language, ALGOL 68RS, used to write ELLA.

ELLA has tools to perform:

Design transformation
Symbolic simulations
Formal verification

ELLA is a winner of the 1989 Queen's Award for Technological Achievement.

Sample

Sample originally from ftp://ftp.dra.hmg.gb/pub/ella, public release.

Code for matrix multiplication hardware design verification:

MAC ZIP = ([INT n]TYPE t: vector1 vector2) -> [n][2]t:
  [INT k = 1..n](vector1[k], vector2[k]).
     
MAC TRANSPOSE = ([INT n][INT m]TYPE t: matrix) -> [m][n]t:
  [INT i = 1..m] [INT j = 1..n] matrix[j][i].

MAC INNER_PRODUCT{FN * = [2]TYPE t -> TYPE s, FN + = [2]s -> s}
                 = ([INT n][2]t: vector) -> s:
  IF n = 1 THEN *vector[1]
  ELSE *vector[1] + INNER_PRODUCT {*,+} vector[2..n]
  FI.

MAC MATRIX_MULT {FN * = [2]TYPE t->TYPE s, FN + = [2]s->s} =
([INT n][INT m]t: matrix1, [m][INT p]t: matrix2) -> [n][p]s:
BEGIN
  LET transposed_matrix2 = TRANSPOSE matrix2.
OUTPUT [INT i = 1..n][INT j = 1..p]
       INNER_PRODUCT{*,+}ZIP(matrix1[i],transposed_matrix2[j])
END.

TYPE element = NEW elt/(1..20),
     product = NEW prd/(1..1200).

FN PLUS = (product: integer1 integer2) -> product:
  ARITH integer1 + integer2.

FN MULT = (element: integer1 integer2) -> product:
  ARITH integer1 * integer2.

FN MULT_234 = ([2][3]element:matrix1, [3][4]element:matrix2) ->
             [2][4]product:  
  MATRIX_MULT{MULT,PLUS}(matrix1, matrix2).

FN TEST = () -> [2][4]product:
( LET m1 = ((elt/2, elt/1, elt/1),
            (elt/3, elt/6, elt/9)), 
      m2 = ((elt/6, elt/1, elt/3, elt/4), 
            (elt/9, elt/2, elt/8, elt/3),
            (elt/6, elt/4, elt/1, elt/2)).
  OUTPUT
    MULT_234 (m1, m2)
).

COM test: just displaysignal MOC

References

Morison, J. D.; Clarke, A. S. (1 October 1993). Ella 2000: A Language for Electronic System Design. McGraw Hill. ISBN 978-0077078218.
Barringer, H.; Gough, G.; Monahan, B.; Williams, A.; Arcus, M.; Armstrong, A.; Hill, M. (1995). "A design and verification environment for ELLA". Design Automation Conference (DAC) 1995. pp. 685–690. doi:10.1109/ASPDAC.1995.486387. ISBN 4-930813-67-0.
Morison, J. D.; Peeling, N. E.; Thorp, T. L.; Whiting, E. V. (1987). "EASE: A Design Support Environment for the HDDL ELLA". Design Automation Conference (DAC) 1987. pp. 741–749. doi:10.1145/37888.38006. ISBN 0-8186-0781-5.

External links

ELLA source code including the ALGOL 68RS translator

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