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In article <DnrCDH.17u@lut.ac.uk>, "J.Last" <eljl3@dwalin.lut.ac.uk> writes:
|> I use both the FTL Modula-2 compiler for CP/M and the Stony Brook compiler for
|> the PC. In the FTL compiler, this statement was fine:
|> 
|> TYPE Vector: ARRAY [0..10] OF REAL;

Try

  TYPE Vector = ARRAY [0..10] OR REAL;

The one with the : in it is invalid syntax.
-- 

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

seurer@nordruth.rchland.ibm.com (Bill Seurer) wrote:
>In article <DnrCDH.17u@lut.ac.uk>, "J.Last" <eljl3@dwalin.lut.ac.uk> writes:
>|> I use both the FTL Modula-2 compiler for CP/M and the Stony Brook compiler for
>|> the PC. In the FTL compiler, this statement was fine:
>|> 
>|> TYPE Vector: ARRAY [0..10] OF REAL;
>
>Try
>
>  TYPE Vector = ARRAY [0..10] OR REAL;
>
>The one with the : in it is invalid syntax.
>-- 
>
>- Bill Seurer     ID Tools and Compiler Development      IBM Rochester, MN
>  Business: BillSeurer@vnet.ibm.com               Home: BillSeurer@aol.com

Yeah, sorry for this posting. There's a mistake there....full marks you spotted
it. This posting only got half posted for some reason. What I meant to say was:

My FTL M-2 compiler allows me to return structured types like this:

PROCEDURE Thingy(Bob:REAL):StructuredType;

Whereas the StonyBrook DOS compiler won't let me. I have to do:

PROCEDURE Thingy(Bob:REAL;VAR Fred:StructuredType);

Is there a good reason for this?

-- 
  _________    _______________________________    _________
 < ""/_\"" \  /                               \  / ""/_\"" >
 <  (.o.)   \/             Jake Last           \/   (.o.)  >
 <   v~v    /\       eljl3@gimli.lut.ac.uk     /\    v~v   >
 <_________/  \_______________________________/  \_________>
        <http://www.geocities.com/SiliconValley/2915>

J.Last (eljl3@dwalin.lut.ac.uk) wrote:

>My FTL M-2 compiler allows me to return structured types like this:

>PROCEDURE Thingy(Bob:REAL):StructuredType;

>Whereas the StonyBrook DOS compiler won't let me. I have to do:

>PROCEDURE Thingy(Bob:REAL;VAR Fred:StructuredType);

>Is there a good reason for this?

The original Modula-2 compilers, as described in "Programming
in Modula-2" by Niklaus Wirth, did not allow structured
types as function return types.  This followed a tradition
established in Pascal.  Wirth is reported to have said that
this was an implementation restriction rather than a language
rule; nevertheless, the de-facto standard of the time, as
described in PIM3, seemed to suggest that structured types
were not allowed, so that was the rule followed by
compiler-writers who thought they were sticking to the
standard.

In some compilers, the authors decided that this was a
stupid restriction, and introduced functions with structured
return types as a "language extension".  In fact, most
M2 compilers I've seen allow this.

Now that we have a proper M2 standard, the situation has
been clarified: structured return types are in the language,
and compilers should support them.  The catch, of course, is
that the standard is so new that most compilers haven't
caught up with it.

--
Peter Moylan                           peter@ee.newcastle.edu.au
                  http://www.eng.newcastle.edu.au/ee/Moylan.html
OS/2 freeware list at 
      http://www.eng.newcastle.edu.au/ee/Moylan/os2/os2info.html

If your complier doesn't return a structured type (I too used FTL 
on CP/M and StonyBrook on MSDOS) rather than a VAR paramenter you 
can return a pointer. In fact FTL seems to allow OPAQUE 
structured types too, but SBM2 seems to require that all OPAQUE 
TYPES are pointers. 

Jake,

>PROCEDURE Thingy(Bob:REAL):StructuredType;
>
>Whereas the StonyBrook DOS compiler won't let me. I have to do:
>
>PROCEDURE Thingy(Bob:REAL;VAR Fred:StructuredType);
>
>Is there a good reason for this?
No, there isn't. PIM doesn't support structured types as returnvalues
of function procedures. But iso says yes to structured returnvalues.
The reason (but not a good ;-)) may be, that StonyBrooks Modula was
PIM orientated and isn't up to date or up to iso.

Joerg.




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