Re: Prototyping printf()

>Date: Wed, 27 Sep 00 17:13:12 +1000
>From: "Simon Coulter" <shc@flybynight.com.au>
> ...
>I know C simplifies parameter passing by widening or promoting data types
but it still
>has to check the basic data type and handle it accordingly.  I see no real
reason why RPG
>couldn't do the same.  It just has more data types to handle so it has a
bigger case
>statement and it doesn't promote the data types.  The compiler knows how
much storage
>each declared variable occupies, it can't be too difficult to use that
information when
>building the argument list.  The only real difficulty is in deciding
whether the
>arguments occupy contiguous storage or not -- and to support the va_
macros used by
>printf() it should be contiguous.
> ...

Simon, the problem is that RPG has too many different numeric types.  What
should it pass for say 3.5?  RPG could adopt C's rules and only have 2
basic numeric type (integer and double-float), so 3.5 would be passed as
8F.  Or it could say that 3.5 was packed(2,1), or perhaps packed(15,5), or
maybe packed(30,15).  Once the compiler has figured out what the passed
type should be, you're right: it's easy.

By the way, for those who would like to venture into the va_list territory,
it IS possible to call vprintf and vsprintf with a single argument list
(Jim Langston, I don't think it's possible to call printf this way though).
But coding a va_list correctly is extremely difficult in RPG.  (*Much*
worse than doing the formatting yourself using RPG's own capability.)

>>Perhaps someday, ILE will have "externally-described" procedures, and RPG

>Isn't that what EXTPGM accomplishes anyway?  Or did you have something
else in mind?

What I have in mind is the ability for a compiler to extract "prototype"
information from a module or service program, similar to the way Java can
extract information directly from a compiled class.  Just a dream ...

Barbara Morris


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