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Add usage example to tree(3).

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Obtained from:	OpenBSD
MFC after:	2 weeks
Sponsored by:	Klara Inc.
This commit is contained in:
Edward Tomasz Napierala 2019-05-08 18:49:59 +00:00
parent e4c934a516
commit ac0879c396
1 changed files with 75 additions and 1 deletions
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76
share/man/man3/tree.3
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@ -30,7 +30,7 @@
.\"
.\" $FreeBSD$
.\"
.Dd January 24, 2015
.Dd May 8, 2019
.Dt TREE 3
.Os
.Sh NAME
@ -559,6 +559,80 @@ and will be overwritten to provide safe traversal.
The
.Fn RB_EMPTY
macro should be used to check whether a red-black tree is empty.
.Sh EXAMPLES
The following example demonstrates how to declare a red-black tree
holding integers.
Values are inserted into it and the contents of the tree are printed
in order.
Lastly, the internal structure of the tree is printed.
.Bd -literal -offset 3n
#include <sys/tree.h>
#include <err.h>
#include <stdio.h>
#include <stdlib.h>
struct node {
RB_ENTRY(node) entry;
int i;
};
int
intcmp(struct node *e1, struct node *e2)
{
return (e1->i < e2->i ? -1 : e1->i > e2->i);
}
RB_HEAD(inttree, node) head = RB_INITIALIZER(&head);
RB_GENERATE(inttree, node, entry, intcmp)
int testdata[] = {
20, 16, 17, 13, 3, 6, 1, 8, 2, 4, 10, 19, 5, 9, 12, 15, 18,
7, 11, 14
};
void
print_tree(struct node *n)
{
struct node *left, *right;
if (n == NULL) {
printf("nil");
return;
}
left = RB_LEFT(n, entry);
right = RB_RIGHT(n, entry);
if (left == NULL && right == NULL)
printf("%d", n->i);
else {
printf("%d(", n->i);
print_tree(left);
printf(",");
print_tree(right);
printf(")");
}
}
int
main(void)
{
int i;
struct node *n;
for (i = 0; i < sizeof(testdata) / sizeof(testdata[0]); i++) {
if ((n = malloc(sizeof(struct node))) == NULL)
err(1, NULL);
n->i = testdata[i];
RB_INSERT(inttree, &head, n);
}
RB_FOREACH(n, inttree, &head) {
printf("%d\en", n->i);
}
print_tree(RB_ROOT(&head));
printf("\en");
return (0);
}
.Ed
.Sh NOTES
Trying to free a tree in the following way is a common error:
.Bd -literal -offset indent