[net.lang.c] I Do Declare!

cottrell@nbs-vms.ARPA (COTTRELL, JAMES) (08/30/85)

/*
In article <368@persci.UUCP> roman@persci.UUCP writes:
> Either I'm missing the perfectly obvious or I've found something
> that's impossible to declare in C, even though it makes sense.  I'm
> trying to implement a simple finite state machine with states
> represented by C functions.  Each state function would accept some
> input value as an argument and return a pointer to the function
> implementing the next state...

Cheat! Declare your variable as a pointer to funxion returning int
(or char (or void) pointer for sticklers) and then use casts.
Saves a lot of headaches trying to figure out all those types.
With char or void pointers, there ought to be a portable way.

typedef	int	 (*PFI)();
typedef char	*(*PFCP)();	/* for portability sticklers */
typedef void	*(*PFVP)();	/* if available */

int	other();
int	init();			/* initial func */
PFI	state = init;		/* state var */

init(arg)
{
	state = other;		/* no problem to set directly */
	...
	return((int)state);	/* to return we must cast */
	...
	state = (PFI)other(arg);/* must cast to assign */
	...
	(*state)(arg);		/* can be called directly */
	...
	while (state = (PFI)(*state)(arg));	/* until no more funx */
}

Once in a while you get shown the light
In the strangest of places if you look at it right.

	jim		cottrell@nbs
*/
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