An array of function pointers.

[Nathaniel Ingersoll]

In article <414 at ucrmath.UUCP> jantypas at ucrmath.UUCP (John Antypas) writes:
 >drawing lines, circles etc.  We'd like to set up something like a vector table.
 >If the vector table has a NULL in a spot, then the interpreter will use its
 >internal routines instead of faster device specific code.  As an example:
 >
 >vectors[] =	{ dev_line(),
 >		  dev_box(),
 >		  dev_circle(),
 >		  dev_arc(),
 >		  dev_text()
 >		}
 >
 >Thanks.
 >
 >John Antypas -- Soft21 --21st Century Software:
 
 I often have programs where I look up a function based on
 something like user input, and what I usually do is
 similar to:
	/* hjkl character movement ... */

	int	f_left(), f_right(), f_up(), f_down();

	int (*vectors[0200])();

	init_vec() {
		vectors['h'] = f_left;
		vectors['j'] = f_down;
		vectors['k'] = f_up;
		vectors['l'] = f_right;
	}


or, similarly,

#define		CASE1	0
#define		CASE2	1
...
#define		CASEN	N	/* some N */

where some input function returns a CASEx, and then
you can have an array of function pointers like

int (*vectors[how many])() = {
	f_case1,
	f_case2,
	...
};

and go like

	int whatcase, getcase();
	int (*f)(), invalidcase();

	whatcase = getcase();
	if (whatcase >= 0 && whatcase < MAXCASE)
		f = vectors[whatcase];
	else
		f = invalidcase;
	(*f)(...);



Now that I've beaten this to death, good luck.
-- 
Nathaniel Ingersoll
Altos Computer Systems, SJ CA
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