


      TSEARCH(3C)                 (UNIX 5.0)                TSEARCH(3C)



      NAME
           tsearch, tdelete, twalk - manage binary search trees

      SYNTAX
           #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.  The second argument
           is a value from an enumeration data type typedef enum {
           preorder, postorder, endorder, leaf } VISIT; (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
           zero.



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      TSEARCH(3C)                 (UNIX 5.0)                TSEARCH(3C)



      NOTES
           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.

      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.

      SEE ALSO
           bsearch(3C), hsearch(3C), lsearch(3C).

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






























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