| 1 | #ifndef BIGUNSIGNEDINABASE_H |
| 2 | #define BIGUNSIGNEDINABASE_H |
| 3 | |
| 4 | #include "NumberlikeArray.hh" |
| 5 | #include "BigUnsigned.hh" |
| 6 | #include <string> |
| 7 | |
| 8 | /* |
| 9 | * A BigUnsignedInABase object represents a nonnegative integer of size limited |
| 10 | * only by available memory, represented in a user-specified base that can fit |
| 11 | * in an `unsigned short' (most can, and this saves memory). |
| 12 | * |
| 13 | * BigUnsignedInABase is intended as an intermediary class with little |
| 14 | * functionality of its own. BigUnsignedInABase objects can be constructed |
| 15 | * from, and converted to, BigUnsigneds (requiring multiplication, mods, etc.) |
| 16 | * and `std::string's (by switching digit values for appropriate characters). |
| 17 | * |
| 18 | * BigUnsignedInABase is similar to BigUnsigned. Note the following: |
| 19 | * |
| 20 | * (1) They represent the number in exactly the same way, except that |
| 21 | * BigUnsignedInABase uses ``digits'' (or Digit) where BigUnsigned uses |
| 22 | * ``blocks'' (or Blk). |
| 23 | * |
| 24 | * (2) Both use the management features of NumberlikeArray. (In fact, my desire |
| 25 | * to add a BigUnsignedInABase class without duplicating a lot of code led me to |
| 26 | * introduce NumberlikeArray.) |
| 27 | * |
| 28 | * (3) The only arithmetic operation supported by BigUnsignedInABase is an |
| 29 | * equality test. Use BigUnsigned for arithmetic. |
| 30 | */ |
| 31 | |
| 32 | class BigUnsignedInABase : protected NumberlikeArray<unsigned short> { |
| 33 | |
| 34 | public: |
| 35 | // The digits of a BigUnsignedInABase are unsigned shorts. |
| 36 | typedef unsigned short Digit; |
| 37 | // That's also the type of a base. |
| 38 | typedef Digit Base; |
| 39 | |
| 40 | protected: |
| 41 | // The base in which this BigUnsignedInABase is expressed |
| 42 | Base base; |
| 43 | |
| 44 | // Creates a BigUnsignedInABase with a capacity; for internal use. |
| 45 | BigUnsignedInABase(int, Index c) : NumberlikeArray<Digit>(0, c) {} |
| 46 | |
| 47 | // Decreases len to eliminate any leading zero digits. |
| 48 | void zapLeadingZeros() { |
| 49 | while (len > 0 && blk[len - 1] == 0) |
| 50 | len--; |
| 51 | } |
| 52 | |
| 53 | public: |
| 54 | // Constructs zero in base 2. |
| 55 | BigUnsignedInABase() : NumberlikeArray<Digit>(), base(2) {} |
| 56 | |
| 57 | // Copy constructor |
| 58 | BigUnsignedInABase(const BigUnsignedInABase &x) : NumberlikeArray<Digit>(x), base(x.base) {} |
| 59 | |
| 60 | // Assignment operator |
| 61 | void operator =(const BigUnsignedInABase &x) { |
| 62 | NumberlikeArray<Digit>::operator =(x); |
| 63 | base = x.base; |
| 64 | } |
| 65 | |
| 66 | // Constructor that copies from a given array of digits. |
| 67 | BigUnsignedInABase(const Digit *d, Index l, Base base); |
| 68 | |
| 69 | // Destructor. NumberlikeArray does the delete for us. |
| 70 | ~BigUnsignedInABase() {} |
| 71 | |
| 72 | // LINKS TO BIGUNSIGNED |
| 73 | BigUnsignedInABase(const BigUnsigned &x, Base base); |
| 74 | operator BigUnsigned() const; |
| 75 | |
| 76 | /* LINKS TO STRINGS |
| 77 | * |
| 78 | * These use the symbols ``0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ'' to |
| 79 | * represent digits of 0 through 35. When parsing strings, lowercase is |
| 80 | * also accepted. |
| 81 | * |
| 82 | * All string representations are big-endian (big-place-value digits |
| 83 | * first). (Computer scientists have adopted zero-based counting; why |
| 84 | * can't they tolerate little-endian numbers?) |
| 85 | * |
| 86 | * No string representation has a ``base indicator'' like ``0x''. |
| 87 | * |
| 88 | * An exception is made for zero: it is converted to ``0'' and not the |
| 89 | * empty string. |
| 90 | * |
| 91 | * If you want different conventions, write your own routines to go |
| 92 | * between BigUnsignedInABase and strings. It's not hard. |
| 93 | */ |
| 94 | operator std::string() const; |
| 95 | BigUnsignedInABase(const std::string &s, Base base); |
| 96 | |
| 97 | public: |
| 98 | |
| 99 | // ACCESSORS |
| 100 | Base getBase() const { return base; } |
| 101 | |
| 102 | // Expose these from NumberlikeArray directly. |
| 103 | NumberlikeArray<Digit>::getCapacity; |
| 104 | NumberlikeArray<Digit>::getLength; |
| 105 | |
| 106 | /* Returns the requested digit, or 0 if it is beyond the length (as if |
| 107 | * the number had 0s infinitely to the left). */ |
| 108 | Digit getDigit(Index i) const { return i >= len ? 0 : blk[i]; } |
| 109 | |
| 110 | // The number is zero if and only if the canonical length is zero. |
| 111 | bool isZero() const { return NumberlikeArray<Digit>::isEmpty(); } |
| 112 | |
| 113 | /* Equality test. For the purposes of this test, two BigUnsignedInABase |
| 114 | * values must have the same base to be equal. */ |
| 115 | bool operator ==(const BigUnsignedInABase &x) const { |
| 116 | return base == x.base && NumberlikeArray<Digit>::operator ==(x); |
| 117 | } |
| 118 | bool operator !=(const BigUnsignedInABase &x) const { return !operator ==(x); } |
| 119 | |
| 120 | }; |
| 121 | |
| 122 | #endif |