caluhelp.h

将中缀表达式转换为后缀表达式

//======== Copyright(C) ?????????????? All rights reserved! ======
// Copyright contents herein, currently it is not defined!!
// 
// Purpose: Currently no Template supporting!!!
//
// $Date:		$
// $Nokeywords:	$
//----------------------------------------------------------------
// Log:
//----------------------------------------------------------------
// Programmer: wuwenxi
//================================================================

#ifndef __CALUHELP_CPP__
#define __CALUHELP_CPP__

#define ALLOC_ONCE    16
// Fixme: The flow macros should become the enum in the class!!!
#define NUMBER_TYPE   0 
#define OPERATOR_TYPE 1
#define OP_ADD        '+'
#define OP_SUB		  '-'
#define OP_MUL        '*'
#define OP_DIV        '/'
#define OP_LEFT_PAR	  '('
#define OP_RIGHT_PAR  ')'
#define DOT			  '.'
#define NEGATIVE	  '_' // instread _ of - to present the negative number

class Element
{
public:
	float value;
	int   type;
};

class CCaluHelp
{
public:
	// Inner class description queue and stack struct
	class HelpQueue
	{
	public:
		// Constructr, malloc a certain memory, it can be 
		// increment later if the memory is not enough
		HelpQueue( );
		// Destructor
		~HelpQueue( );
		
	public:
		Element& Front( void );
		void     AddToTail( const Element& elem );
		bool     Empty( void ) const;
		int      UsedLength( void ) const;
		int      FreeLength( void ) const;
		
	private:
		Element * m_pMem;
		int       m_nAllocCount;
		Element * m_pStart;
		Element * m_pEnd;
		Element * m_pFree;
	
	private:
		bool   EnsureCapacity( void );
		
	private:
		// Nerver allowed the flow operations
		// in the purpose of the simplely to do
		// Actually, the flow control is not needed
		HelpQueue( const HelpQueue& );
		HelpQueue& operator=( const HelpQueue& );
	};
	
	struct HelpStackNode
	{
		Element value;
		HelpStackNode * next;
	};
	
	class HelpStack
	{
	public:
		// Constructor, Destructor
		HelpStack( );
		~HelpStack( );
		
	public:
		void    Push( const Element & elem );
		Element Pop( void ); // delete the node
		void    PopMatch( const Element & elem, HelpStack& stack );
		bool    Empty( void ) const;
		void    ClearStack( void );
		
	private:
		HelpStackNode * m_Top;
	
	private:
		void    Clear( void );
	};
	
	//
	// Operations
	//
	float      CaluExpr( const char * pcszExpr );
	
private:
	// Gen Postfix expr ( 将pszExpr代表的中缀表达式转换为后缀表达式 )
	void       ParseExpr( const char * pcszExpr, HelpQueue& queue );
	// 根据后缀表达式计算最后结果
	float      CaluPostfix( HelpQueue& postfixQueue );
	
};

#endif // __CALUHELP_CPP__