Re: Prototyping printf()

[Jim Langston <jlangston@xxxxxxxxxxxxxxxx>]

The ellipses in the printf prototype is just a mechanic to allow any number of 
parameters.  It would be possible to emulate the same thing in RPG with creative
pointer and string control.

What C does with the printf and parameters is handled by the subroutine itself,
not the compiler.  As someone mentioned there is a lot of work that has to be 
done
in the procedure to pull the parameters off the stack.

If you think about how you could pass pointers to an RPG function (think of 
passing
them as strings) you should realize that you could do the same thing calling 
the 
printf function!

It's a bit of a kludge, but say I wanted to call something like:

printf("The string is %s and the number is %i\n", SomeString, SomeNumber);

C really doesn't care what parameters you pass it.  In this case we are passing
2 pointers and a integer value (not positive if %i is correct for integer, but 
you
get the point).  The first pointer is to the constant we declared, which still 
gets
passed as a pointer, the second is to the variable SomeString.  The third is the
binary SomeNumber.  What if you just build this all in one string?

I don't want to work out all the mechanics right here but may later, but 
something
like

C     Eval   PassString = StrPoint%("The string is %s and the number is %i\n") +
C                         StrPoint%(SomeString) + StrInt(SomeNumber)

C     CallP  PrintF(PassString)

In theory StrPoint would return the pointer address to the string as a string, 
and StrInt
would return the binary value of the integer as a string.  Very easy if you 
think about it.

D              DS
D StrPointer             P  1   4
D ReturnStr              A  1   4

I'm not saying it's easy, nor desirable, just possible.  RPG allows us to do 
the same fudging
of pointers and variable types as C does, through data structures and pointers.

Regards,

Jim Langston
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