twalk() — Binary tree walk

Standards

Standards / Extensions	C or C++	Dependencies
XPG4 XPG4.2 Single UNIX Specification, Version 3	both

Format

#define _XOPEN_SOURCE
#include <search.h>

void *twalk(const void *root, void (*action)(const void *, VISIT, int));

General description

The twalk() function traverses a binary search tree. The root argument is a pointer to the root node of the tree to be traversed. (Any node in a tree may be used as the root for a walk below that node.) The argument 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 structure pointed to by this argument is unspecified and must not be modified by the application, but is guaranteed that a pointer-to-node can be converted to pointer-to-pointer-to-element to access the element stored in the node. The second argument is a value from an enumeration data type:

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

(defined in the <search.h> header), depending on whether this is the first, second or third time that the node is 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.

Threading Behavior: see tsearch() — Binary tree search.

Special behavior for C++: Because C and C++ linkage conventions are incompatible, twalk() cannot receive a C++ function pointer as the argument. If you attempt to pass a C++ function pointer to twalk(), the compiler will flag it as an error. You can pass a C or C++ function to twalk() by declaring it as extern C.

Returned value

twalk() returns no values.

No errors are defined.