bugged calculator..

[Sendy Hipo]

hi im trying to do Bjarne Stroustrup's exercise (calculator), it worked well but when im trying to add new function in the calculator (add new variable) it has bugs..
its not complete yet, because when i checked a bit, after i add string "name" inside Token class, it gives no answer ("nan"). then i checked and test each functions, it seems the problem is in the primary() function, it doesn't return what it should does, i already check using std::cout inside the switch statement(it gives the right token's value), but when it returns the value to the term() function (to the double left specificly, and yes i checked left with std::cout and i found the that primary function return the wrong value) the valuue is "nan", i cant figure out why this goes wrong , anyone can help?
here's the code :

please do check on primary () function

sorry for the long code

 
#include <iostream>

#include <cctype>
#include "std_lib_facilities.h"



const char number = '8';
const char print = ';';
const char quit = 'q';
const char test = 'a';
const char let = 'L';

class Token
{
    public:
    char kind;
    double value;
    string name;

    Token(char k, String n)
    {
        kind = k;
        name = n;
        value = 0;
    }

    Token(char k, double v)
    {
        kind = k;
        value = v;
        name = "";
    }
    Token(char k)
    {
        kind = k;
        value = 0;
    }
    Token(double v)
    {
        kind = number;
        value = 0;
    }
    Token(String s)
    {
        name = s;
    }
    Token()
    {
        kind = number;
        value = 0;
    }


};class Token_Stream
{
    private :
    bool full;
    Token buffer;

    public:
    void ignore()
    {
        if(full == true && buffer.kind == print)
        {
            full = false;
            return;
        }

        full = false;

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

    }
    Token_Stream() : full(false), buffer(0.0){}

    void put_back(Token t)
    {
        buffer = t;
        full = true;
    }
    Token get()
    {
        if(full == true)
        {
            full = false;
            return buffer;
        }
        char ch;
        std::cin>>ch;
        switch(ch)
        {
            case '!':
            case print:
            case quit:
            case '(':
            case ')':
            case '+':
            case '-':
            case '*':
            case '/':
            case '%':
            case '{':
            case '}':
            return Token(ch);

            case '.':
            case '0':
            case '1':
            case '2':
            case '3':
            case '4':
            case '5':
            case '6':
            case '7':
            case '8':
            case '9':
            {
                std::cin.putback(ch);// taro char balik ke istream
                double value;
                std::cin>>value;//smua yang ad di istream(yang tadi d putback) d masukin ke value

                return Token(number, value);
            }
            default :

                        if(isalpha(ch))
                        {
                            String temp;
                            temp += ch;
                            while((std::cin.get(ch) && isalpha(ch)) ||isdigit(ch))
                            {
                                temp += ch;
                            }
                            std::cin.putback(ch);
                            if(temp == "let")
                            {
                                return Token(let);
                            }
                            if(temp == "quit")
                            {
                                return Token(test);
                            }



                        }
                        error("bad token!");
            }
    }
};

Token_Stream ts;


void calculate();
double expression();
double term();
double primary();
double fact(double);
void clean_up_mess();





int main()
{
    try
    {
        calculate();
        return 0;
    }
    catch(runtime_error &e)
    {
        std::cerr<<e.what();
        std::cout<<"enter '~' to continue \n";
        keep_window_open("~");
    }
    return 0;
}


void calculate()
{
    while(std::cin)
    {
        try
        {
            Token t;
            std::cout<<"> ";
            t = ts.get();
            while(t.kind == print)//discard all "prints" (';')
            {
                t = ts.get();
            }

            if(t.kind == quit)
            {
                return;
            }
            ts.put_back(t);
            std::cout<<"the answer is = "<<expression()<<std::endl;
        }
        catch(exception &e)
        {
            std::cerr<<e.what()<<std::endl;
            ts.ignore();
        }
    }
}


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.put_back(t);
                      return left;
        }
    }
}

double term()
{
    double left = primary();
    std::cout<<left<<std::endl;//check the value that's returned from primary , it says "nan"

    Token t = ts.get();

    while(true)
    {
        switch(t.kind)
        {
            case '!' :
            {
                double x = left;
                left *= fact(x-1);t = ts.get();break;
            }

            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 d = narrow_cast<int>(left);
                        int d2 = narrow_cast<int>(primary());
                        if(d2 == 0)
                        {
                            error("cannot divide by zero");
                        }
                        left = d % d2;
                        t = ts.get();
                        break;
                    }
            case '{':
            case '(': ts.put_back(t);
                       left *= primary();
                       t = ts.get();
                       break;

            default : ts.put_back(t);
                      return left;
        }
    }
}

double primary()
{
    Token x = ts.get();

    switch(x.kind)
    {
        case '(' :
               {
                   std::cout<<"case (\n";
                   double d = expression();
                   x = ts.get();
                   if(x.kind != ')')
                   {
                       error("error expected ) !");
                   }
                   return d;
               }
        case '{':std::cout<<"case {\n";
                {
                    double d = expression();
                   x = ts.get();
                   if(x.kind != '}')
                   {
                       error("error expected } !");
                   }
                   return d;
                }
        case number: std::cout<<x.value<<std::endl; //i check the value here
                     return x.value;break;
        case '+' :std::cout<<"case +\n"; return primary();
        case '-' :std::cout<<"case -\n"; return -primary();

        default  : error("expected primary expression");

    }
}

double fact(double x)
{
    if(x>0)
    return x * fact(x-1);
    else
    return 1;
}

its not complete yet, because everytime i make a bit change, i always check.
if i remove string name from the class Token , the calculator works well.

[j2NvC542]

I have some error in a header file now, but it should work on windows. I have done the same exercise and I could pastebin it if you want, so you can compare with yours.

[Sendy Hipo]

erm sure
actually i know that the problem is (what i think) from the primary function that's not returning the right value, do you know why this happens?

[viliml]

What is the error?

[j2NvC542]

This is my output:

> 1+3;
1
1
3
3
the answer is = 4

This is on Windows XP with Visual C++ 2010 Express. I assume you use that IDE too?

I have no idea how it outputs "nan". Really.

[Sendy Hipo]

guys i just tried using visual c++ 2010 and it works, before i used codeblocks (windows).
now the question is why in codde blocks it(the code, specificly in primary () function) returns "nan"?

[j2NvC542]

Build log in Codeblocks:

/usr/lib/gcc/x86_64-redhat-linux/4.6.3/../../../../include/c++/4.6.3/bits/locale_facets_nonio.h:1902:5: error: template-id ‘do_get<>’ for ‘String std::messages<char>::do_get(std::messages_base::catalog, int, int, const String&) const’ does not match any template declaration
/usr/lib/gcc/x86_64-redhat-linux/4.6.3/../../../../include/c++/4.6.3/bits/locale_facets_nonio.h:1902:62: note: saw 1 ‘template<>’, need 2 for specializing a member function template

Build messages:

/usr/lib/gcc/x86_64-redhat-linux/4.6.3/../../../../include/c++/4.6.3/bits/locale_facets_nonio.h|1902|error: template-id ‘do_get<>’ for ‘String std::messages<char>::do_get(std::messages_base::catalog, int, int, const String&) const’ does not match any template declaration|
/usr/lib/gcc/x86_64-redhat-linux/4.6.3/../../../../include/c++/4.6.3/bits/locale_facets_nonio.h|1902|note: saw 1 ‘template<>’, need 2 for specializing a member function template|

Can we see your std_lib_facilities.h?

[Sendy Hipo]

erm sure, actually i just make new header files and copy all contents from :

http://stroustrup.com/Programming/std_lib_facilities.h

to my new header file which i named "std_lib_facilities.h"