1.#QNAN0,gcc vc6.0 的区别

[hlyces]

gcc-4.4.2-32

下：[2240] term:return value:1.#QNAN0

vc 6.0

下：[2244] term:return value:1.000000

/* Copyright(C)
 * For free
 * All right reserved
 * 
 */
/** 
 * @file main.cpp
 * @brief calculator
 * @author hlyces, [e-mail]
 * @version 1.0
 * @date 2010-01-16
 */
#include "std_lib_facilities.h"

#include <windows.h>

class Token{
	public:
		char kind;
		double value;
		string name;
		Token(char ch)
			:kind(ch),value(0){}
		Token(char ch, double val)
			:kind(ch),value(val){}
		Token( char ch, string n): kind( ch), name( n){}
};

class Token_stream
{
	public:
		Token_stream( ):full( false),buffer( 0){

		}
		Token get( );
		void putback( Token t);
		void ignore( char c);
	private:
		bool full;
		Token buffer;
};

class Variable{
	public:
		string name;
		double value;
		Variable( string n, double v):name( n),value( v){}
};

const string prompt = ">";
const string result = "=";
const string declkey= "let";
const char let = 'L';
const char name = 'a';
const char print = ';';
const char quit = 'q';
const char number = '8';
vector <Variable> var_table;
Token_stream ts;



double expression();

double term();

double primary();

double get_value( string s);

void set_value( string s, double d);

double statement( );

bool is_declared( string var);

double define_name(  string var, double val);

double declaration( );

void Token_stream::putback( Token t)
{
	OutputDebugString("putback..");
	if( full) error( "putback( ) into a full buffer");
	buffer=t;
	full=true;
}	

Token Token_stream::get( )
{
	if( full)
	{
		full=false;
		return buffer;
	}
	char ch;
	cin >> ch;
	switch( ch){
		case quit:
		case print:
		case '(':
		case ')':
		case '+':
		case '-':
		case '*':
		case '/':
		case '%':
			OutputDebugString("get operator");
			return Token( ch);
		case '.':
		case '0': case '1': case '2': case '3': case '4':
		case '5': case '6': case '7': case '8': case '9':
			{
				cin.putback( ch);
				double val;
				cin >> val;
				OutputDebugString("get number");
				return Token( number,val);
			}
		case '=':
			OutputDebugString("get '='");
			return Token(ch);
		default :
			if( isalpha( ch))
			{
				string s;
				s+=ch;
				while( cin.get( ch) &&( isalpha( ch)||isdigit( ch)))
					s+=ch;	
				if( s == declkey) 
				{
					OutputDebugString("get 'let'");
					return Token( let);
				}
				cin.putback(ch);
				return Token( name, s);
			}
			error( "Bad token");
	}
}

void Token_stream::ignore( char c)
{
	if( full && c==buffer.kind)
	{
		full = false;
		return;
	}
	full=false;

	char ch=0;
	while( cin>>ch)
		if( ch==c) return;
}





double get_value( string s)
{
	for( int i=0; i<var_table.size( ); ++i)
		if( var_table[i].name==s)
		{
			return	var_table[i].value;
		}
	error( "get : undefined Variable",s);
}

void set_value( string s, double d)
{
	for( int i=0; i<var_table.size( );++i)
		if( var_table[i].name==s) 
		{
			var_table[i].value=d;
			return;
		}
	error( "set : undefined Variable",s);

}

bool is_declared( string var)
{
	for( int i=0; i<var_table.size( ); ++i)
		if( var_table[i].name==var) return true;
	return false;
}

double define_name( string var, double val)
{
	if( is_declared( var)) error( var," declared twice");
	var_table.push_back( Variable( var,val));
	return val;
}

double declaration( )
{
	Token t=ts.get( );
	if( t.kind!=name) error( "name expected in declaration");
	string var_name=t.name;

	Token t2=ts.get( );

	if( t2.kind!='=') error( "missing '=' in declaration of ",var_name);

	double d = expression( );
	define_name( var_name, d);
	return d;
}

double statement( )
{
	Token t=ts.get( );
	switch( t.kind)
	{
		case let:
			return declaration( );
		default:
			ts.putback( t);
			return expression( );
	}
}





double expression()
{
	double left=term();
	Token t=ts.get();
	while( true)
	{
		switch(t.kind)
		{
			case '+' :
				left+=term( );
				t=ts.get( );
				break;
			case '-' :
				left-=term( );
				t=ts.get( );
				break;
			default:
				ts.putback( t);
				char buffer[30];
			sprintf(buffer,"expression:return value:%f",left);
			OutputDebugString(buffer);
				return left;
		}
	}
}
double term()
{
	double left=primary();
	Token t=ts.get();
	while( true)
	{
		switch(t.kind)
		{
			case '*' :
				left*=primary( );
				t=ts.get( );
				break;
			case '/' :
				{

					double d=primary( );
					if( d == 0) error( "divide by zero");
					left/=d;
					t=ts.get( );
					break;
				}
			case '%' :
				{
					int i1=narrow_cast<int>( left);
					int i2=narrow_cast<int>(term());
					if( i2==0) error( "%:divide by zero");
					left=i1%i2;
					t= ts.get( );
					break;
				}
			default:
				ts.putback( t);
char buffer[30];
			sprintf(buffer,"term:return value:%f",left);
			OutputDebugString(buffer);
				return left;
		}
	}
}

double primary()
{
	Token t=ts.get();
	switch(t.kind)
	{
		case '(' :
			{
				double d=expression( );
				t=ts.get( );
				if( t.kind!=')') error("')' expected") ;
				return d;
			}	
		case number :
			char buffer[30];
			sprintf(buffer,"primary:return value:%f",t.value);
			OutputDebugString(buffer);
			return t.value;
		case '-':
			return - primary( );
		case '+':
			return primary( );
		default:
			error( "primary expected");
	}

}



void clean_up_mess( )
{
	ts.ignore( print);
	//system("cls");
}

void calculate( )
{
	while(cin)
	{
		try{
			cout << prompt;
			Token t = ts.get();
			while( t.kind == print) t=ts.get( );
			if( t.kind == quit) 
			{
				return ;	
			}
			ts.putback( t);
			cout << result << statement( ) << endl;
		}
		catch( exception & e)
		{
			cerr << e.what( ) << endl;
			clean_up_mess( );
		}
	}
}



int main()
{
	try
	{
		calculate( );
		keep_window_open( );
		return 0;
	}
	catch( exception & e)
	{
		cerr << e.what( ) << endl;
		keep_window_open( "~~");
		return 1;
	}
	catch(...)
	{
		cerr << "exception \n" ;
		keep_window_open( "~~");
		return 2;
	}
}

[hlyces]

[Quote=引用 4 楼 laowu_ 的回复:]
哪里越界嘞
不晓得,你试了下喽
[/Quote]
在gcc下
你有没试？？
输入1+2;
会得到=nan
而在VC下是
=3

[hlyces]

/*
	simple "Programming: Principles and Practice using C++" course header to
	be used for the first few weeks.
	It provides the most common standard headers (in the global namespace)
	and minimal exception/error support.

Students: please don't try to understand the details of headers just yet:
	All will be explained. This header is primarily used so that you don't have
	to understand every concept all at once.
*/

#ifndef H112
#define H112 201001L

#include<iostream>
#include<fstream>
#include<sstream>
#include<cmath>
#include<cstdlib>
#include<string>
#include<vector>
#include<algorithm>
#include<stdexcept>
using namespace std;

const string s="";
template<class T> string to_string(const T& t)
{
	ostringstream os;
	os << t;
	return os.str();
}

struct Range_error : out_of_range {	// enhanced vector range error reporting
	int index;
	Range_error(int i) :out_of_range("Range error: "+to_string(i)), index(i) { }
};




struct Exit : runtime_error {
	Exit(): runtime_error("Exit") {}
};

// error() simply disguises throws:
inline void error(const string& s)
{
	throw runtime_error(s);
}

inline void error(const string& s, const string& s2)
{
	error(s+s2);
}

inline void error(const string& s, int i)
{
	ostringstream os;
	os << s <<": " << i;
	error(os.str());
}



template<class T> char* as_bytes(T& i)	// needed for binary I/O
{
	void* addr = &i;	// get the address of the first byte
						// of memory used to store the object
	return static_cast<char*>(addr); // treat that memory as bytes
}


inline void keep_window_open()
{
//	cin.clear();
//	cout << "Please enter a charcter to exit\n";
	system("pause");
//	char ch;
//	cin >> ch;
	return;
}

inline void keep_window_open(string s)
{
	if (s=="") return;
	cin.clear();
	cin.ignore(120,'\n');
	for (;;) {
		cout << "Please enter " << s << " to exit\n";
		string ss;
		while (cin >> ss && ss!=s)
			cout << "Please enter " << s << " to exit\n";
		return;
	}
}

// make std::min() and std::max() accessible:
#undef min
#undef max

#include<iomanip>
inline ios_base& general(ios_base& b)	// to augment fixed and scientific
{
	b.setf(ios_base::fmtflags(0),ios_base::floatfield);
	return b;
}

// run-time checked narrowing cast (type conversion):
template<class R, class A> R narrow_cast(const A& a)
{
	R r = a;
	if (A(r)!=a) error(string("info loss"));
	return r;
}


inline int randint(int max) { return rand()%max; }

inline int randint(int min, int max) { return randint(max-min)+min; }

#endif

[老吴笔记]

百度一下,你就知道
Google一下,你就知道的太多了

[hlyces]

...

我在VC下能得到正解


gcc下却说越界？？


是不是double 要写成long double?

[老吴笔记]

哪里越界嘞
不晓得,你试了下喽

[cocat]

好长噢~帮顶