🚀 go-pugleaf

mfx@cs.tu-berlin.de (Markus Freericks) writes:

>In article <3vl6b2$dne@solutions.solon.com> seebs@solutions.solon.com (Peter Seebach) writes:
>> >- what if you _want_ one or all results to be undefined?
>> 
>> Give a real-world example, and I'll worry about it.

>A function that determines the intersection between two line segments,
>determined by four float arguments (two points) each, returning an enum
>flag (no intersection / one point intersection / line segment intersection)
>and four float results, of which either none, two, or all four are
>defined.

You cannot return multiple values in C anyway, so this is moot. You
can return a structure and are free to initialize only some of its
fields. And you are also free to change or not change locations to
which pointers are passed to the function. Both possibilities cover
your example:

typedef enum {NONE; POINT, LINE} intdesc_t;
typedef struct { 
    intdesc_t type;
    float x1, y1, x2, y2;
} intersect_t;

intersect_t intersection1 (float l1x1, float l1y1, float l1x2, float l1y2,
			  float l2x1, float l2y1, float l2x2, float l2y2);

intdesct_t intersection2 (float l1x1, float l1y1, float l1x2, float l1y2,
			  float l2x1, float l2y1, float l2x2, float l2y2,
			  float *ix1, float *iy1, float *ix2, float *iy2);

	hp
--
   _  | Peter Holzer | Systemadministrator WSR | hjp@wsr.ac.at
|_|_) |-------------------------------------------------------
| |   |  ...and it's finished!  It only has to be written.
__/   |         -- Karl Lehenbauer