Hidden routines

[Dave Jones]

> I want to write a subroutine in C, called S.  I want S to be known outside.
> I also want to have two subroutines X and Y to be known ONLY to S 
> (not known outside of S).  Either can be called by S, and each calls 
> the other in a recursive way.  I also need to share several variables
> entirely within this context (shared between S, X, Y).  They can be 
> static.  There will only be 1 instance of S (and therefore also of X
> and Y, but that should be hidden).  Main program M should be able to 
> call S, but any references to X and Y will not be resolved by the 
> module S. How do I lay out the arrangement of source for S?  An 
> example would be appreciated.  Thanks.

You should read a textbook on C programming. I recommend the classic
Kerningham and Richie.

The only reason I am answering is that I saw some really awful advice in
another reply. 

(That sounded a little grumpy. It was not meant to be.)

Now then... The instructions are contradictory. 

   "two subroutines X and Y to be known ONLY to S"
   "each calls the other in a recursive way"
   "any references to X and Y will not be resolved by the module S"

Hum. The way I interpret it, here's what you want:

static foo X();
static foo Y();

static foo A;

static
X()
{
  A = Y();
}

static
Y()
{
  A = X();
}

S()
{
  A = X();
  A = Y();
}


Complile main() in a separate file and declare S() as "extern" in
that file.