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Talk:K-d tree: Difference between revisions
→C Entry: stylistic things
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Line 43:
kd_node_t *right;
};</lang>
: 1) In terms of decoupling struct defs and usage, the easiest thing is probably
:<lang c>void swap(struct kd_node_t *x, struct kd_node_t *y)
{
struct kd_node_t tmp;
tmp = *x;
*x = *y;
*y = tmp;
}</lang> which hides the details best, but does unnecessary copying. Another way is
:<lang c>struct point_t { double x[3]; }
struct kd_node_t {
point_t pt;
struct kd_node_t *left, *right;
}
void swap(struct kd_node_t *x, struct kd_node_t *y)
{
point_t tmp;
tmp = x->pt;
x->pt = y->pt;
y->pt = tmp;
}</lang> which is arguably better, because it now allows the compiler to figure out the best method to do the copying. The thing is, hiding details from <code>swap()</code> is not right. Being a performance critical part, it ''should'' know the inner working of the struct involved. You could also argue that one shouldn't do <code>node->x[1]</code>, instead some accessor method <code>get_node_coord(node, 1)</code> should be used. If we were designing a library and plan for it to be used by total strangers who need an interface decoupled from data definition, maybe; for a short example on RC and a samll routine used internally, no.
: 2) I'm ambivalent towards use of <code>NULL</code> token (it's probably <code>#define NULL (0)</code> anyway), which is better than what I have to say about <code>TRUE</code> or <code>FALSE</code>. If one is reading C code, he better know what a nul pointer is anyhow. I prefer writing <code>0</code>, but won't mind if someone changes it to <code>NULL</code>.
: 3) The <code>typedef</code> is indeed unneeded. My habit is <code>typedef struct {} sometype_t</code> and <code>typedef struct {} *sometype</code>, where <code>_t</code> says it's a struct, and lacking of it means a pointer. This may make pointers to pointers easier to write (<code>sometype *p</code> instead of <code>sometype_t **p</code>), but is certainly not necessary. I'll drop the <code>typedef</code>s here, but I doubt it will make the code more or less readable. --[[User:Ledrug|Ledrug]] 21:34, 26 April 2012 (UTC)
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