// Arbitrarily large numbers
//
// A LargeNumber object should from any external point store its unsigned
// number in positional code in the range [0..sig] of its number array.
// This code should always lack leading 0s except when representing zero itself.
// If the represented number is negative then the negative flag should be set
// otherwise it should not be set.  The max should be equal to one less than
// the number array size and sig should never be greater than max.
//
// Author  Matthew Caryl
// Created 13.3.97

#include <iostream.h>

class LargeNumber
{
    public:
    LargeNumber(void);
    LargeNumber(long n);
    LargeNumber(const LargeNumber& n);
    ~LargeNumber(void);
    
    char to_char(void) const;
    short to_short(void) const;
    int to_int(void) const;
    long to_long(void) const;
    
    bool even(void) const;
    bool odd(void) const;
    int length(void) const; // in bits
    bool bit(unsigned int p) const; // p'th bit (from zero)
    bool zero() const; // is zero
    bool sign(void) const; // is negative
    
    void truncate(int n); // reduce to lower n bits
    void complement(void); // * -1
    
    bool operator==(const LargeNumber& n) const;
    bool operator!=(const LargeNumber& n) const;
    bool operator<(const LargeNumber& n) const;
    bool operator<=(const LargeNumber& n) const;
    bool operator>(const LargeNumber& n) const;
    bool operator>=(const LargeNumber& n) const;
    
    LargeNumber& operator=(const LargeNumber& n);
    LargeNumber& operator+=(const LargeNumber& n);
    LargeNumber& operator-=(const LargeNumber& n);
    LargeNumber& operator<<=(int n);
    LargeNumber& operator>>=(int n);
    LargeNumber& operator++(void);
    LargeNumber& operator--(void);
    LargeNumber  operator++(int);
    LargeNumber  operator--(int);
    LargeNumber& operator*=(const LargeNumber& n);
    LargeNumber& operator/=(const LargeNumber& n);
    LargeNumber& operator%=(const LargeNumber& n);
    // no change of sign for following operators
    LargeNumber& operator&=(const LargeNumber& n);
    LargeNumber& operator|=(const LargeNumber& n);
    LargeNumber& operator^=(const LargeNumber& n);
    
    LargeNumber operator+(const LargeNumber& n) const;
    LargeNumber operator-(const LargeNumber& n) const;
    LargeNumber operator*(const LargeNumber& n) const;
    LargeNumber operator/(const LargeNumber& n) const;
    LargeNumber operator%(const LargeNumber& n) const;
    // no change of sign for following operators
    LargeNumber operator&(const LargeNumber& n) const;
    LargeNumber operator|(const LargeNumber& n) const;
    LargeNumber operator^(const LargeNumber& n) const;
    LargeNumber operator<<(int n) const;
    LargeNumber operator>>(int n) const;
    
    friend ostream& operator<<(ostream& s, const LargeNumber& n);
    friend istream& operator>>(istream& s, LargeNumber& n);
    
    private:
    char* number;
    bool negative;
    int sig;
    int max;
    
    // unsigned operators
    bool smaller(const LargeNumber& n) const; // unsigned
    bool greater(const LargeNumber& n) const; // unsigned
    void expand(int n); // ensure n'th bit exits
    void contract(); // remove leading 0s
    void plus(const LargeNumber& n); // unsigned
    void minus(const LargeNumber& n); // unsigned
};