Libc-825.24.tar.gz

[apple/libc.git] / stdlib / FreeBSD / tsearch.3

diff --git a/stdlib/FreeBSD/tsearch.3 b/stdlib/FreeBSD/tsearch.3
index d7121d4bdd64a82b73e4fa8c37c2eb0b2baa7357..9d7a863206aab5ab83f221f707437dbfdcb3e1d3 100644 (file)
--- a/stdlib/FreeBSD/tsearch.3
+++ b/stdlib/FreeBSD/tsearch.3
@@ -31,18 +31,36 @@
 .Dt TSEARCH 3
 .Os
 .Sh NAME
-.Nm tsearch , tfind , tdelete , twalk
+.Nm tdelete ,
+.Nm tfind ,
+.Nm tsearch ,
+.Nm twalk
 .Nd manipulate binary search trees
 .Sh SYNOPSIS
 .In search.h
 .Ft void *
-.Fn tdelete "const void * restrict key" "void ** restrict rootp" "int (*compar) (const void *, const void *)"
+.Fo tdelete
+.Fa "const void *restrict key"
+.Fa "void **restrict rootp"
+.Fa "int (*compar) (const void *key1, const void *key2)"
+.Fc
 .Ft void *
-.Fn tfind "const void *key" "void * const *rootp" "int (*compar) (const void *, const void *)"
+.Fo tfind
+.Fa "const void *key"
+.Fa "void *const *rootp"
+.Fa "int (*compar) (const void *key1, const void *key2)"
+.Fc
 .Ft void *
-.Fn tsearch "const void *key" "void **rootp" "int (*compar) (const void *, const void *)"
+.Fo tsearch
+.Fa "const void *key"
+.Fa "void **rootp"
+.Fa "int (*compar) (const void *key1, const void *key2)"
+.Fc
 .Ft void
-.Fn twalk "const void *root" "void (*action) (const void *, VISIT, int)"
+.Fo twalk
+.Fa "const void *root"
+.Fa "void (*action) (const void *node, VISIT order, int level)"
+.Fc
 .Sh DESCRIPTION
 The
 .Fn tdelete ,
@@ -50,39 +68,46 @@ The
 .Fn tsearch ,
 and
 .Fn twalk
-functions manage binary search trees based on algorithms T and D
+functions manage binary search trees, based on algorithms T and D
 from Knuth (6.2.2).
 The comparison function passed in by
-the user has the same style of return values as
+the user takes two arguments, each of which is a key
+pointer.
+This function has the same style of return values as
 .Xr strcmp 3 .
 .Pp
 The
 .Fn tfind
 function
-searches for the datum matched by the argument
+searches for a node whose key matches the argument
 .Fa key
 in the binary tree rooted at
 .Fa rootp ,
-returning a pointer to the datum if it is found and NULL
+returning a pointer to the node if it is found and NULL
 if it is not.
 .Pp
+Note that a node is itself a pointer to the key of the node.
+Thus, you should generally cast this result to a
+double pointer to the data type stored in the tree, for example
+(struct myType **), and use double indirection to retrieve the
+original key value.
+.Pp
 The
 .Fn tsearch
-function
-is identical to
+function is identical to
 .Fn tfind
-except that if no match is found,
+except that, if no match is found,
+it inserts a new node for the
 .Fa key
-is inserted into the tree and a pointer to it is returned.
+into the tree and returns a pointer to the node.
 If
 .Fa rootp
-points to a NULL value a new binary search tree is created.
+points to a NULL value, a new binary search tree is created.
 .Pp
 The
 .Fn tdelete
-function
-deletes a node from the specified binary search tree and returns
-a pointer to the parent of the node to be deleted.
+function deletes a node from the specified binary search tree
+and returns a pointer to the parent of the node that was deleted.
 It takes the same arguments as
 .Fn tfind
 and
@@ -93,20 +118,44 @@ will be adjusted.
 .Pp
 The
 .Fn twalk
-function
-walks the binary search tree rooted in
+function walks the binary search tree rooted in
 .Fa root
 and calls the function
 .Fa action
 on each node.
 The
 .Fa action
-function
-is called with three arguments: a pointer to the current node,
+function is called with three arguments: a pointer to the current node,
 a value from the enum
 .Sy "typedef enum { preorder, postorder, endorder, leaf } VISIT;"
 specifying the traversal type, and a node level (where level
 zero is the root of the tree).
+.Pp
+As
+.Fn twalk
+traverses the tree, it calls the
+.Fa action
+function with the traversal type "preorder"
+before visiting the left subtree of the
+.Fa node ,
+with the
+traversal type "postorder" before visiting the right subtree
+of the
+.Fa node ,
+and with the traversal type "endorder" after
+visiting the right subtree of the
+.Fa node .
+.Pp.
+The
+.Fa action
+function is called only once for a leaf-node, with the
+traversal type "leaf."
+.Pp
+Note: the names for the traversal types differ somewhat from
+common parlance.  The traversal type "postorder" corresponds
+to what would typically be referred to as in-order, and the
+traversal type "endorder" corresponds to what would typically
+be referred to as post-order.
 .Sh RETURN VALUES
 The
 .Fn tsearch
@@ -121,7 +170,7 @@ and
 functions
 return NULL if
 .Fa rootp
-is NULL or the datum cannot be found.
+is NULL or the node cannot be found.
 .Pp
 The
 .Fn twalk