TSEARCH(3C)             COMMAND REFERENCE             TSEARCH(3C)



NAME
     tsearch, tdelete, twalk - manage binary search trees

SYNOPSIS
     #include <search.h>

     char *tsearch ((char *) key, (char **) rootp, compar)
     int (*compar)( );

     char *tdelete ((char *) key, (char **) rootp, compar)
     int (*compar)( );

     void twalk ((char *) root, action)
     void (*action)( );

DESCRIPTION
     Tsearch is a binary tree search routine generalized from
     Knuth (6.2.2) Algorithm T.  It returns a pointer into a tree
     indicating where a datum may be found.  If the datum does
     not occur, it is added at an appropriate point in the tree.

     Key points to the datum to be sought in the tree.

     Rootp points to a variable that points to the root of the
     tree.  A NULL pointer value for the variable denotes an
     empty tree; in this case, the variable will be set to point
     to the datum at the root of the new tree.

     Compar is the name of the comparison function.  It is called
     with two arguments that point to the elements being
     compared.  The function must return an integer less than,
     equal to, or greater than zero according as the first
     argument is to be considered less than, equal to, or greater
     than the second.

     Tdelete deletes a node from a binary search tree.  It is
     generalized from Knuth (6.2.2) algorithm D.  The arguments
     are the same as for tsearch.  The variable pointed to by
     rootp will be changed if the deleted node was the root of
     the tree.  Tdelete returns a pointer to the parent of the
     deleted node, or a NULL pointer if the node is not found.

     Twalk traverses a binary search tree.

     Root is the root of the tree to be traversed.  (Any node in
     a tree may be used as the root for a walk below that node.)

     Action is the name of a routine to be invoked at each node.
     This routine is, in turn, called with three arguments.

     The first argument is the address of the node being visited.




Printed 3/13/89                                                 1

TSEARCH(3C)             COMMAND REFERENCE             TSEARCH(3C)



          NOTE:   This is not the address of the data in the
                  tree; it is a pointer to that address.

     The second argument is a value from an enumeration data
     type:

          typedef enum { preorder, postorder, endorder, leaf }
          VISIT;

     It is defined in the <search.h> header file, depending on
     whether this is the first, second, or third time that the
     node has been visited (during a depth-first, left-to-right
     traversal of the tree), or whether the node is a leaf.

     The third argument is the level of the node in the tree,
     with the root being level 0.

DIAGNOSTICS
     A NULL pointer is returned by tsearch if there is not enough
     space available to create a new node.

     A NULL pointer is returned by tsearch and tdelete if rootp
     is NULL on entry.

CAVEATS
     The pointers to the key and the root of the tree should be
     of type pointer-to-element, and cast to type pointer-to-
     character.

     The comparison function need not compare every byte, so
     arbitrary data may be contained in the elements in addition
     to the values being compared.

     Although declared as type pointer-to-character, the value
     returned should be cast into type pointer-to-element.

          WARNING:  The root argument to twalk is one level of
                    indirection less than the rootp arguments to
                    tsearch and tdelete.nentry.

     Awful things can happen if the calling function alters the
     pointer to the root.

SEE ALSO
     bsearch(3c), hsearch(3c), intro(3), and lsearch(3c).










Printed 3/13/89                                                 2

%%index%%
na:336,104;
sy:440,2176;
de:2616,2140;5164,685;
di:5849,540;
ca:6389,1074;
se:7463,210;
%%index%%000000000121