Re: Prototyping printf()

h
Hello Barbara,

You wrote:
>C can support the ellipsis because it has only has 3 basic types: int,
>double, pointer.  No matter what it sees as a parameter, it knows what
>to actually put on the parameter stack (*usually* what the programmer
>intended.  'a' gets passed as a 4-byte int, 1.3 gets passed as a double,
>"abcde" gets passed as a pointer.  The problem is that RPG has many
>more basic types than RPG does.

I don't see more data types as being the root of the problem.  Variables are 
simply 
n-bytes at x-address regardless of the type (pointers are 16, ints are 2 or 4, 
floats are 
4 or 8, etc.).  The problem is that prototypes requires a data type.  

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. 

        ---- useful example code deleted ------

>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?

>will have good support for variable-typed parameters.  I don't think
>printf and its dot-dot-dot friends are a good model for this, though.

Perhaps not, but it seems there is sufficient interest in such a facility (even 
with the 
simple syntax I described earlier) for it to move up the ToDo list.  Now how 
WILL I spend 
my $100 ....

Regards,
Simon Coulter.

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