[Oberon] open array usage

[Chris Burrows]

>From: oberon-bounces at lists.inf.ethz.ch 
>[mailto:oberon-bounces at lists.inf.ethz.ch] On Behalf Of 
>Aubrey.McIntosh at Alumni.UTexas.Net
>Sent: Sunday, 11 July 2010 10:56 AM

>
>In reading the compiler and system source, I have seen 
>statements of the form
>
>  InitStruct (s1, "this", 42, "that");
>  InitStruct (s2, "another", 43, "item");
>  InitStruct (s3, "more", 44, "again")
>

Yes - that is a good example of the general case where the array is an array
of something other than a basic type. 

I have seen a similar 'divide and conquer' approach used when 

a) the array is an array of a basic type
b) there are a large number of items
c) there is no discernible sequence or pattern allowing loop initialisation
to be used

e.g. r: ARRAY 200 OF REAL;

The 'helper' procedure looks like:

PROCEDURE Init(VAR r: ARRAY OF REAL; offset: INTEGER; d0, d1, d2, d3, d4,
d5, d6, d7, d8, d9: REAL);
BEGIN
  r[offset] := d0; 
  r[offset+1] := d1;
...
END Init;

and the initialisation sequence is then something like:

Init(r,  0,   1.0,  3.0,  5.0,  7.0,  9.0,  2.0,  4.0,  4.1,  2.1,  4.3);
Init(r, 10,  11.0, 31.0, 15.0, 27.0, 91.0, 42.0, 34.0, 24.1, 12.1, 34.3);
Init(r, 20,  11.1, 31.6, 14.0, 21.0, 31.0, 42.6, 31.0, 20.1, 11.1, 30.3);
....
....
Init(r,190,  11.0, 31.0, 15.0, 27.0, 91.0, 42.0,  4.0,  4.1,  2.1,  4.3);

What might otherwise have been 200 statements is reduced to 30 statements.

However, in many cases where you have a large number of constant values used
for initialisation the numbers are read in from a file, a registry, a
resource etc. etc. rather than being hard-coded constants.

Regards,
Chris Burrows
CFB Software

Astrobe: ARM Oberon-07 Development System
http://www.astrobe.com