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erico@cnmat.berkeley.edu (Eric Obermuhlner) wrote:
> How do I make constant tables?
> 
> I write code for an embedded system. Lookup tables in ROM are a 
pretty useful thing and I just couldn't find a way to do it.
> 
> Did I miss something?
> 
> Something like
> [BEGIN EXAMPLE]
> VAR
>   myTable : ARRAY [0..9] OF CARDINAL = [0, 6, 2, 5, 1, 3, 4, 9, 
8, 7];
> [END EXAMPLE]

Hmm, havn't been doing much MODULA programming lately, but from 
what I take from the MODULA standard, it would be something like:

MODULE example;
TYPE
  CA = ARRAY [0..9] OF CARDINAL;

CONST
  myTable = CA({0, 6, 2, 5, 1, 3, 4, 9, 8, 7});

...

though I can't garantee that the braces ({}) are correct.

-Robert
-- 
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Robert Frank                                        
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Please try to keep your lines a bit shorter :-)

> How do I make constant tables?
> 
> I write code for an embedded system. Lookup tables in ROM are a pretty 
> useful thing and I just couldn't find a way to do it.

Depending on your compiler, you may find the literal data being put in an 
unexpected segment, and then copied to a literal constant. It is 
sometimes easier to put this sort of thing into a fixed location in 
memory, accessed by an absolute variable.

> Did I miss something?
> 
> Something like
> [BEGIN EXAMPLE]
> VAR
>   myTable : ARRAY [0..9] OF CARDINAL = [0, 6, 2, 5, 1, 3, 4, 9, 8, 7];
> [END EXAMPLE]

Depends very much on the compiler. Under TopSpeed (which we use for 
embedded '386):

TYPE    tableType= ARRAY[0..9] OF CARDINAL;

CONST   myTable= tableType(0, 6, 2, 5, 1, 3, 4, 9, 8, 7);

Mark Morgan Lloyd
mark_tbu@cix.compulink.co.uk

[Opinions above are the author's, not those of his employers or 
colleagues]

Constant tables were non-standard in earlier versions of Modula-2.  Some
allowed it (like TopSpeed) anyway.

The new standard allows it but I don't know of any compilers.
-- 

- Bill Seurer     ID Tools and Compiler Development      IBM Rochester, MN
  Business: BillSeurer@vnet.ibm.com               Home: BillSeurer@aol.com

Bill Seurer wrote:
> 
> Constant tables were non-standard in earlier versions of Modula-2.  Some
> allowed it (like TopSpeed) anyway.
> 
> The new standard allows it but I don't know of any compilers.
> --
> 
> - Bill Seurer     ID Tools and Compiler Development      IBM Rochester, MN
>   Business: BillSeurer@vnet.ibm.com               Home: BillSeurer@aol.com

Sure, all the native code versions of gpm allow this.
Furthermore, in code (as opposed to constant declarations)
you can write

	blah := MyType{exp1, exp2, ..., expN};

where exp1, exp2 are any expressions.  The compiler extracts
the constant parts at compile time, and fills in the variable
parts at runtime.

John Gough