ELLA (programming language)

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 originally from ftp://ftp.dra.hmg.gb/pub/ella^{[dead link]}, public release.

Code for matrix multiplication hardware design verification:

MAC ZIP = (TYPE t: vector1 vector2) -> t:
  (vector1, vector2).
     
MAC TRANSPOSE = (TYPE t: matrix) -> t:
    matrix.

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

MAC MATRIX_MULT {FN * = TYPE t->TYPE s, FN + = s->s} =
(t: matrix1, t: matrix2) -> s:
BEGIN
  LET transposed_matrix2 = TRANSPOSE matrix2.
OUTPUT 
       INNER_PRODUCT{*,+}ZIP(matrix1,transposed_matrix2)
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 = (element:matrix1, element:matrix2) ->
             product:  
  MATRIX_MULT{MULT,PLUS}(matrix1, matrix2).

FN TEST = () -> 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

• ELLA source code including the ALGOL 68RS translator

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