#ifndef CalcFace_SEEN
#define CalcFace_SEEN
///////    File CalcFace.h    ///////
#include    <iostream.h>
#include    <ctype.h>

// function input: returns op in c and input number if any
//     return value == OPONLY means only op is entered
//     return value == OFF means no more input 

class CalcFace
{   public:
        CalcFace( const int digs,    // calculator precision
                  const char* k      // operation keys recognized
                );
        virtual int input(char& c, double& number, int err);
        virtual void show_number(double number);
        virtual void show_error()
        {   cerr << "Error" << endl;   }
        virtual void show_op(char op) { }
        virtual int err_input(char& op);
        enum {OPONLY = 1, OFF};
        ~CalcFace() { delete nbuf;  }
    protected:
        virtual int inchar()
        {  return(cin.get()); }
        virtual void extract_number(double&);
        virtual void build_number(char c, int& i);
        int nump(char c);
        char*         nbuf;     // buffer[prec+2] for input number
        const char*   keys;     // keys
        const int     prec;     // precision
};
#endif