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From: Robert Dewar <robert_dewar@my-deja.com>
Subject: Re: Question about interfacing C and Ada95
Date: 1999/11/09
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References: <806ud0$lu1$1@trog.dera.gov.uk>
 <zDFV3.101$Wi2.9657@typhoon-sf.snfc21.pbi.net>
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Date: 1999-11-09T00:00:00+00:00
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In article <zDFV3.101$Wi2.9657@typhoon-sf.snfc21.pbi.net>,
  tmoran@bix.com wrote:
> >we have recoded the c to this as Ada funcs do not allow more
than
> >one return val;
> >
> >void getX ( void **instance, int *float, int *error );
> >
> >How do I then write the Ada to interface to this in Ada 95.
>   procedure getX(M     : in out Matrix;
>                  Float : in out integer;
>                  Error : out integer);
> or so, depending on just what you want.
>   Actually, both Ada and C allow a single return value from a
> function, ie "result = getX(....);", but Ada in addition
allows
> "out" or "in out" parameters to procedures, which in C must be
> simulated by passing "in" a pointer to the target parameter.


Note incidentally, that, following the DEC ADa 83 design, GNAT
provides value returning procedures that allow modeling of
external functions with out parameters. See description of
Import_Valued_Procedure pragma in DEC or GNAT documentation.


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