ELLA (programming language)

ELLA is a Hardware description language and support toolset. Developed by the Royal Signals and Radar Establishment during the 1980s and 90s.

Includes 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 (a now dead link) - 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

See also

• Ella 2000: A Language for Electronic System Design - by J. D. Morison, A. S. Clarke
• A design and verification environment for ELLA - Barringer, Gough, Monahan, Williams, Arcus, Armstrong & Hill. - IEEE Xplore, Volume, Issue, 29 Aug-1 Sep 1995 Page(s):685 - 690
• EASE : A design support environment for the HDDL ELLA - J D Morison, N E Peeling, T L Thorp, E V Whiting - ACM/IEEE Design Automation Conference, 1987 pp741-749

External links

• [1] ELLA source code including the ALGOL 68RS translator.