Calculation

[ogranatw]

I am a beginner and I need help writing a calculation program.
The program should be able to handle at least 8 operators, square, sin, cos, tan, powers, +, -, *, /.
The program should be able to handle all these things in one expression.

For example: v for square, s for sin, c for cos, t for tan and ^ for power. v(s3.4/5^8). T
he program needs to understand parenthesis. And square, sin, cos and tan should be used as a "prefix" (executed on the following operator).
And when '=' is put in the result is written out, the program resets and restarts.

And if you could put in some comentaries in the code, so I know waht you've dont. It would be very helpful for the future.

Please help me!!!

Thank you

[Duoas]

Unfortunately, no one here is going to do your homework for you.

I don't know why CS 101/102 professors continue to give this as homework. It is not a particularly simple thing to do.

You might want to google around "recursive descent".

Good luck.

[Graham]

It is NOT simple, at all.

For a while, I've tried to do this, and have never succeded...

If you get a clue, contact me. I'd love to know.

PS: See the book listed in my Bio, it has an exercise after chapter 12 describing how to do this in detail.

[mezosoft]

hello i'm mo3taz from egypt,
i,ve solved this problem but just for the operators +,-;
example input: 1+2+3-2+3-4+5.
out put: the result
don't forget the fullstop at the end

# include <iostream.h>
int main()
{
int sum = 0; 
int x , y;                                     // two successive numbers in the input between them
char test = 'r';                           // an operator
char op;                                    // stands for an operator
while (test == 'c' || test == 'r') // tests for continue(c) or restart (r)
{
 if ( test == 'r')
 {
  sum = 0;
  cout << "___________________________________________________________________";
  cout << "\nplease enter some successive numbers between each two an operator\n";
  cout << "the equation encludes just '+' or '-' ( example:1+2-3+4.) \n";
 }
 if (test == 'c')
  {
  cout << " please enter another sequence to add to the old sequence\n";
  cout << "the old value was : " << sum << endl;
  }
 cin >> x;
 cin >> op;
 cin >> y;
 if (op == '+')
  sum = (sum + x + y);
 else if ( op == '-')
  sum = (sum + x - y);

 while (op != '.')

  {
   cin >> op;
   if (op == '.') break ;  // notice that the operator may be '.'
   cin >> y ;              // after entering the while loop
   if (op == '+')
   sum = (sum + y);
   else if (op == '-')
   sum = (sum - y);

  }

  cout <<"the result of this sequenc is: \n:" << sum << endl;
  cout << "please enter c to continue calculating to the old result\n";
  cout << "please enter r to restart and calculate a new value\n";
  cout << " please enter e to exit \n ";
  cin>> test;
  if (test == 'e')
  break;
  }
}

if there is any problem with this tell me , and i'll try to insert other operators
my e_mail is : [e-mail]

[wooden nose]

There is a way to solve this problem with a recurive descent:

I have *fully* copied this code from Arnold Willemers page (http://www.willemer.de/informatik/cpp/rekursion.htm)
But you can also find it in one of his books.

enum tToken 
{
    PLUS, MINUS, MUL, DIV, LPAR, RPAR, NUMBER, END, ERROR
};

// Globale Variablen:
tToken aktToken;        // das zuletzt erkannte Token
double TokenZahlenWert; // der Wert bei Zahlenkonstanten

char *srcPos;           // Programm-Position

tToken sucheToken()
// Sucht ab der aktuellen Stringposition das nächste Token.
// Hier werden auch die Zahlenkonstanten bestimmt und in
// der globalen Variablen TokenZahlenWert abgelegt.
{
    aktToken = ERROR;
    if (*srcPos==0)
    {
        aktToken = END;
    } 
    else 
    {
        switch (*srcPos)
        {
            case '(': aktToken=LPAR;  break;
            case ')': aktToken=RPAR;  break;
            case '*': aktToken=MUL;   break;
            case '/': aktToken=DIV;   break;
            case '+': aktToken=PLUS;  break;
            case '-': aktToken=MINUS; break;
        }
        if (*srcPos>='0' && *srcPos<'9') 
        {
            aktToken=NUMBER;
            TokenZahlenWert = 0.0;
        }
        while (*srcPos>='0' && *srcPos<'9') 
        {
            TokenZahlenWert *= 10;
            TokenZahlenWert += *srcPos-'0';
            srcPos++;
        }
        if (aktToken != NUMBER)
        {
            srcPos++;
        }
    }
    return aktToken;
}

tToken Error(char *s)
// Meldung ausgeben und Fehler-Token zurückliefern
{
    cerr << s << endl;
    return ERROR;
}

double PlusMinus(); // Prototyp

double Klammern()
// wertet Klammern, Zahlen und Vorzeichen aus
// ruft Klammern() und PlusMinus() dadurch rekursiv auf!
{
    double Wert;
    switch(aktToken)
    {
        case NUMBER:
            sucheToken();
            return TokenZahlenWert;
        case MINUS:
            sucheToken();
            return -Klammern();
        case LPAR:
            sucheToken();
            Wert = PlusMinus();
            if (aktToken != RPAR)
            {
               return Error(") expected");
            {
            sucheToken();
            return Wert;
        case END:
            return 1;
    }
    return Error("primary expected");
}

double MulDiv()
// wertet Multiplikation und Division aus
// ruft Klammern() auf, dadurch rekursiv!
{
    double Wert;
    // rufe erst die Operation mit der nächsthöheren
    // Priorität auf
    Wert = Klammern();
    while (aktToken==MUL || aktToken==DIV)
    {
        if (aktToken==MUL)
        {
            sucheToken();
            Wert *= Klammern();
        }
        else if (aktToken==DIV)
        {
          sucheToken();
          Wert /= Klammern();
        }
    }
    return Wert;
}

double PlusMinus()
// wertet Summe und Differenz aus
// ruft MulDiv() auf, dadurch rekursiv
{
    double Wert;
    // rufe erst die Operation mit der nächsthöheren
    // Priorität auf
    Wert = MulDiv();
    while (aktToken==PLUS || aktToken==MINUS)
    {
        if (aktToken==PLUS)
        {
            sucheToken();
            Wert += MulDiv();
        }
        else if (aktToken==MINUS)
        {
            sucheToken();
            Wert -= MulDiv();
        }
    }
    return Wert;
}

double Auswertung(char *s)
{
    srcPos = s;
    sucheToken();      // bestimme das erste Token vorweg
    return PlusMinus();
}

int main(int argc, char* argv[])
{
    double Wert = Auswertung(argv[1]);
    cout << Wert << endl;
    return 0;
}

its in german, sorry for that :)

It loops trough all token and looks what it is and then calls the needed function.



Hope it helps

wooden nose

[ogranatw]

Thanks for your help, you've been vary helpful.