[Oberon] Procedure variables and local procedures

[Jörg]

Wojtek

> I am guessing that Chris has the above in mind. I second his opinion: without the dynamic arrays (or "open arrays") the language is crippled.

Oberon-07 has open arrays.
Open arrays are formal parameters whose length is not known at compile time.

Here an example in Oberon-07:

  PROCEDURE Max(v: ARRAY OF REAL): REAL; (* ‚v‘ is an open array *)
     VAR i: INTEGER; max: REAL;
     BEGIN
        max := v[0];
        FOR i := 1 TO LEN(v)-1 DO IF v[i]>max THEN max := v[i] END END
     RETURN max END Max;

and use Max() with vectors of different lengths like
     v1: ARRAY 10 OF REAL;
     v2: ARRAY 88 OF REAL;

If you would like to write a library operating on two dimensional matrices, you can do so in Oberon-07. It is left as an exercise how to implement

  MODULE Matrix;
  TYPE
    Matrix* = POINTER TO MatrixDesc;
    MatrixDesc = RECORD
       m*: PROCEDURE (i, j: INTEGER): REAL (* m(i, j) returns an elem of the matrix *)
    END;
  PROCEDURE Allocate*(m: Matrix; dim1, dim2: INTEGER);
  PROCEDURE Initialize*(m: Matrix; f: Files.File);
  PROCEDURE EigenValue*(m: Matrix): REAL;
  END Matrix.

As all this is possible in Oberon-07, I was wondering what dynamic arrays are.

br
Jörg