deskcalc.cpp???

hi guys,
i have been trying to make this thing work .heres the code for calculator by the way. Everything compiles fine except for push_back(). heres the code snippet.

Code:

 Token_value get_token()
{
char ch ;
   do{
    if(!cin.get(ch)) return curr_tok = END;
     }while(ch !=( '/n' && isspace(ch)) ) ;

  switch(ch){
  case ';' :
  case '\n' :
           return curr_tok = PRINT ;

default : // NAME, NAME = , or error

 if( isalpha(ch)){
        string_value =  ch ;
       while( cin.get(ch) && isalnum (ch)) string_value.push_back(ch) ;//HERES THE ERROR. 
        cin.putback(ch);
        return  curr_tok = NAME ;
        }
    error("bad token");
    return curr_tok = PRINT ;
 }
}

THE COMPILER ERROR:->
53 deskcalc.cpp no matching function for call to `basic_string<char,string_char_traits<char>,__default_alloc_template<false,0> >::push_back (char &)'

push_back does take char . doesnt it?? if theres any mistake then please let me know. Atleast i will be able to learn from my mistake.
iostream , cctype, string, map has already been included.Map is needed to create a table of strings.

-> means "p"

What's string_value declared as?

a string

Well what do you expect push_back to do? It's not a method of string. Do you want ch appended onto the end of string_value? Do: string_value += ch;

heres the code (full)

Code:

// deskcalc.cpp by "B. Stroustrup"

#include <iostream>
#include <cctype>
#include <map>
#include <string>


using namespace std;



double expr(bool);
double number_value ;
string string_value;
double term(bool);
double prim(bool);
map<string,double>table ;


 enum Token_value {
           NAME        ,  NUMBER ,  END ,
           PLUS = '+' , MINUS = '-', MUL = '*' ,DIV = '/' ,
           PRINT = ';' , ASSIGN = '=' ,LP = '(' , RP = ')'
 };

 Token_value curr_tok = PRINT ;

 int no_of_errors;

double error(const string& s)
 {
 no_of_errors++ ;
 cerr<< "error: "<< s << '/n' ;
 return 1 ;
 }
 Token_value get_token()
{
char ch ;
   do{
    if(!cin.get(ch)) return curr_tok = END;
     }while(ch !=( '/n' && isspace(ch)) ) ;

  switch(ch){
  case ';' :
  case '\n' :
           return curr_tok = PRINT ;

default : // NAME, NAME = , or error

 if( isalpha(ch)){
        string_value =  ch ;
        while( cin.get(ch) && isalnum (ch))  
       string_value.push_back(ch) ; 
                 // ch would be pushed in  string_value . isnt it???
        cin.putback(ch);
        return  curr_tok = NAME ;
        }
    error("bad token");
    return curr_tok = PRINT ;
 }
}




 double expr(bool get) // add and subtract
 {

  double left = term (get) ;
  for(; ;)
         switch (curr_tok) {
   case PLUS :
            left += term(true);
            break;
   case MINUS:
            left -= term(true);
            break;
   default :
            return left ;
   }
}



double term(bool get)
{
 double left = prim(get);
   for(; ;)
    switch(curr_tok){
    case MUL:
             left *= prim(true);
             break;
    case DIV:
            if(double d = prim(true) ){
                  left /= d;
                  break;
            }

            return (error("divide by 0"));

    default:
            return left;
       }

}


double prim(bool get)
{
      if(get)  get_token();

      switch(curr_tok) {
      case NUMBER : //floating point constant
      {
       double v = number_value ;
       get_token();
       return v ;
      }
      case NAME :
      {
       double& v = table[string_value];
       if(get_token() == ASSIGN ) v = expr(true);
       return v;
      }
      case MINUS: // unary minus
      {return -prim(true);}
      case LP:
      {double e = expr(true);
       if(curr_tok != RP) return error("')' expected ") ;
        get_token();
        return e ;
        }
      default :
        return error("primary expected");

      }
}


 int main()
 {
 table["pi"] = 3.14159 ;
 table["e"] = 2.7182 ;
 while(cin)
  {
  get_token();
  if(curr_tok == END ) break ;
  if(curr_tok == PRINT ) continue ;
  cout << expr(false) <<'\n';
   }
  return no_of_errors ;
 }

i tried your way Eibro but it isnt working. ~:- (

is ";"

I think B. stroustrup didnt see his mistakes. Isn't it Eibro?

You might want to invest in learning how to click the box that says 'disable smilies in this post'

It works fine for me when I change the direction of the newline characters here

Code:

cerr<< "error: "<< s << '/n' ;

and here

Code:

}while(ch !=( '/n' && isspace(ch)) ) ;

Don't forget that the newline character is a backslash followed by lower case n: '\n' :-)

>>Well what do you expect push_back to do? It's not a method of string.
Since when? The standard shows it right between the append and assign methods at the end of page 385. :-)

Code:

void push_back(const charT);