Question

是的，我正试图从Larry Nyhoff的书中获取这些代码，以便在Bloodshed中编译。它实际上是从作者的网站上逐字逐句采用的，虽然我在.cpp上声明它而不是.h（.h文件不适用于测试人员应用程序）。

http://cs.calvin.edu/activities/books/c++/ds/2e/SourcePrograms/Chap12/

搜索（const DataType＆amp; item）功能让我感到悲伤。编译器错误说：

In member function `bool BST<DataType>::search(const DataType&) const': 
expected `;' before "locptr" 
`locptr' undeclared (first use this function)

我在这里错过了什么？

 #include <iostream>

#ifndef BINARY_SEARCH_TREE
#define BINARY_SEARCH_TREE


template <typename DataType>
class BST
{
 public:
  /***** Function Members *****/
  BST();

  bool empty() const;

  bool search(const DataType & item) const;

  void insert(const DataType & item);

  void remove(const DataType & item);

  void inorder(std::ostream & out) const;

  void graph(std::ostream & out) const;

  private:
  /***** Node class *****/
  class BinNode 
  {
   public:
    DataType data;
    BinNode * left;
    BinNode * right;

    // BinNode constructors
    // Default -- data part is default DataType value; both links are null.
    BinNode()
    : left(0), right(0)
    {}

    // Explicit Value -- data part contains item; both links are null.
    BinNode(DataType item)
    : data(item), left(0), right(0)
    {}


}; //end inner class

typedef BinNode * BinNodePointer; 

  /***** Private Function Members *****/
  void search2(const DataType & item, bool & found,
               BinNodePointer & locptr, BinNodePointer & parent) const;
 /*------------------------------------------------------------------------
   Locate a node containing item and its parent.

   Precondition:  None.
   Postcondition: locptr points to node containing item or is null if 
       not found, and parent points to its parent.#include <iostream>
 ------------------------------------------------------------------------*/

  void inorderAux(std::ostream & out, 
                  BST<DataType>::BinNodePointer subtreePtr) const;
  /*------------------------------------------------------------------------
    Inorder traversal auxiliary function.

    Precondition:  ostream out is open; subtreePtr points to a subtree 
        of this BST.
    Postcondition: Subtree with root pointed to by subtreePtr has been
        output to out.
 ------------------------------------------------------------------------*/

  void graphAux(std::ostream & out, int indent,
                      BST<DataType>::BinNodePointer subtreeRoot) const;
  /*------------------------------------------------------------------------
    Graph auxiliary function.

    Precondition:  ostream out is open; subtreePtr points to a subtree 
        of this BST.
    Postcondition: Graphical representation of subtree with root pointed 
        to by subtreePtr has been output to out, indented indent spaces.
 ------------------------------------------------------------------------*/

 /***** Data Members *****/
  BinNodePointer myRoot; 

}; // end of class template declaration

//--- Definition of constructor
template <typename DataType>
inline BST<DataType>::BST()
: myRoot(0)
{}

//--- Definition of empty()
template <typename DataType>
inline bool BST<DataType>::empty() const
{ return myRoot == 0; }

//--- Definition of search()
template <typename DataType>
bool BST<DataType>::search(const DataType & item) const
{
   BST<DataType>::BinNodePointer locptr = myRoot; //**THIS FAILS, WHY?**//
   bool found = false;
   while (!found && locptr != 0)
   {
      if (item < locptr->data)       // descend left
        locptr = locptr->left;
      else if (locptr->data < item)  // descend right
        locptr = locptr->right;
      else                           // item found
        found = true;
   }
   return found;
}




#endif

Answer 1

在声明前加上typename：

typename BST<DataType>::BinNodePointer locptr = myRoot;

关键是由于潜在的模板特化，编译器无法知道依赖标识符BinNodePointer标识了类型。

让最好的模板工作

1 个答案: