BigUnsigned( short x);
protected:
// Helpers
- template <class X> void initFromPrimitive(X x);
+ template <class X> void initFromPrimitive (X x);
template <class X> void initFromSignedPrimitive(X x);
public:
protected:
// Helpers
template <class X> X convertToSignedPrimitive() const;
- template <class X> X convertToPrimitive() const;
+ template <class X> X convertToPrimitive () const;
public:
- // ACCESSORS
+ // BIT/BLOCK ACCESSORS
// Expose these from NumberlikeArray directly.
NumberlikeArray<Blk>::getCapacity;
/* Returns the requested block, or 0 if it is beyond the length (as if
* the number had 0s infinitely to the left). */
Blk getBlock(Index i) const { return i >= len ? 0 : blk[i]; }
+ /* Sets the requested block. The number grows or shrinks as necessary. */
+ void setBlock(Index i, Blk newBlock);
// The number is zero if and only if the canonical length is zero.
bool isZero() const { return NumberlikeArray<Blk>::isEmpty(); }
+ /* Returns the length of the number in bits, i.e., zero if the number
+ * is zero and otherwise one more than the largest value of bi for
+ * which getBit(bi) returns true. */
+ Index bitLength() const;
+ /* Get the state of bit bi, which has value 2^bi. Bits beyond the
+ * number's length are considered to be 0. */
+ bool getBit(Index bi) const {
+ return (getBlock(bi / N) & (1 << (bi % N))) != 0;
+ }
+ /* Sets the state of bit bi to newBit. The number grows or shrinks as
+ * necessary. */
+ void setBit(Index bi, bool newBit);
+
// COMPARISONS
// Compares this to x like Perl's <=>
void bitAnd(const BigUnsigned &a, const BigUnsigned &b);
void bitOr(const BigUnsigned &a, const BigUnsigned &b);
void bitXor(const BigUnsigned &a, const BigUnsigned &b);
- void bitShiftLeft(const BigUnsigned &a, unsigned int b);
- void bitShiftRight(const BigUnsigned &a, unsigned int b);
+ /* Negative shift amounts translate to opposite-direction shifts,
+ * except for -2^(8*sizeof(int)-1) which is unimplemented. */
+ void bitShiftLeft(const BigUnsigned &a, int b);
+ void bitShiftRight(const BigUnsigned &a, int b);
/* `a.divideWithRemainder(b, q)' is like `q = a / b, a %= b'.
* / and % use semantics similar to Knuth's, which differ from the
BigUnsigned operator &(const BigUnsigned &x) const;
BigUnsigned operator |(const BigUnsigned &x) const;
BigUnsigned operator ^(const BigUnsigned &x) const;
- BigUnsigned operator <<(unsigned int b) const;
- BigUnsigned operator >>(unsigned int b) const;
- // Additional operators in an attempt to avoid overloading tangles.
- // XXX Why exactly are these needed?
BigUnsigned operator <<(int b) const;
BigUnsigned operator >>(int b) const;
void operator &=(const BigUnsigned &x);
void operator |=(const BigUnsigned &x);
void operator ^=(const BigUnsigned &x);
- void operator <<=(unsigned int b);
- void operator >>=(unsigned int b);
- // Additional operators in an attempt to avoid overloading tangles.
- // XXX Why exactly are these needed?
void operator <<=(int b);
void operator >>=(int b);
return ans;
}
inline BigUnsigned BigUnsigned::operator /(const BigUnsigned &x) const {
+ if (x.isZero()) throw "BigUnsigned::operator /: division by zero";
BigUnsigned q, r;
r = *this;
r.divideWithRemainder(x, q);
return q;
}
inline BigUnsigned BigUnsigned::operator %(const BigUnsigned &x) const {
+ if (x.isZero()) throw "BigUnsigned::operator %: division by zero";
BigUnsigned q, r;
r = *this;
r.divideWithRemainder(x, q);
ans.bitXor(*this, x);
return ans;
}
-inline BigUnsigned BigUnsigned::operator <<(unsigned int b) const {
+inline BigUnsigned BigUnsigned::operator <<(int b) const {
BigUnsigned ans;
ans.bitShiftLeft(*this, b);
return ans;
}
-inline BigUnsigned BigUnsigned::operator >>(unsigned int b) const {
+inline BigUnsigned BigUnsigned::operator >>(int b) const {
BigUnsigned ans;
ans.bitShiftRight(*this, b);
return ans;
}
-inline BigUnsigned BigUnsigned::operator <<(int b) const {
- if (b < 0)
- throw "BigUnsigned::operator <<(int): Negative shift amounts are not allowed";
- return *this << (unsigned int)(b);
-}
-inline BigUnsigned BigUnsigned::operator >>(int b) const {
- if (b < 0)
- throw "BigUnsigned::operator >>(int): Negative shift amounts are not allowed";
- return *this >> (unsigned int)(b);
-}
inline void BigUnsigned::operator +=(const BigUnsigned &x) {
add(*this, x);
multiply(*this, x);
}
inline void BigUnsigned::operator /=(const BigUnsigned &x) {
+ if (x.isZero()) throw "BigUnsigned::operator /=: division by zero";
/* The following technique is slightly faster than copying *this first
* when x is large. */
BigUnsigned q;
*this = q;
}
inline void BigUnsigned::operator %=(const BigUnsigned &x) {
+ if (x.isZero()) throw "BigUnsigned::operator %=: division by zero";
BigUnsigned q;
// Mods *this by x. Don't care about quotient left in q.
divideWithRemainder(x, q);
inline void BigUnsigned::operator ^=(const BigUnsigned &x) {
bitXor(*this, x);
}
-inline void BigUnsigned::operator <<=(unsigned int b) {
+inline void BigUnsigned::operator <<=(int b) {
bitShiftLeft(*this, b);
}
-inline void BigUnsigned::operator >>=(unsigned int b) {
+inline void BigUnsigned::operator >>=(int b) {
bitShiftRight(*this, b);
}
-inline void BigUnsigned::operator <<=(int b) {
- if (b < 0)
- throw "BigUnsigned::operator <<=(int): Negative shift amounts are not supported";
- *this <<= (unsigned int)(b);
+
+/* Templates for conversions of BigUnsigned to and from primitive integers.
+ * BigInteger.cc needs to instantiate convertToPrimitive, and the uses in
+ * BigUnsigned.cc didn't do the trick; I think g++ inlined convertToPrimitive
+ * instead of generating linkable instantiations. So for consistency, I put
+ * all the templates here. */
+
+// CONSTRUCTION FROM PRIMITIVE INTEGERS
+
+/* Initialize this BigUnsigned from the given primitive integer. The same
+ * pattern works for all primitive integer types, so I put it into a template to
+ * reduce code duplication. (Don't worry: this is protected and we instantiate
+ * it only with primitive integer types.) Type X could be signed, but x is
+ * known to be nonnegative. */
+template <class X>
+void BigUnsigned::initFromPrimitive(X x) {
+ if (x == 0)
+ ; // NumberlikeArray already initialized us to zero.
+ else {
+ // Create a single block. blk is NULL; no need to delete it.
+ cap = 1;
+ blk = new Blk[1];
+ len = 1;
+ blk[0] = Blk(x);
+ }
}
-inline void BigUnsigned::operator >>=(int b) {
- if (b < 0)
- throw "BigUnsigned::operator >>=(int): Negative shift amounts are not supported";
- *this >>= (unsigned int)(b);
+
+/* Ditto, but first check that x is nonnegative. I could have put the check in
+ * initFromPrimitive and let the compiler optimize it out for unsigned-type
+ * instantiations, but I wanted to avoid the warning stupidly issued by g++ for
+ * a condition that is constant in *any* instantiation, even if not in all. */
+template <class X>
+void BigUnsigned::initFromSignedPrimitive(X x) {
+ if (x < 0)
+ throw "BigUnsigned constructor: "
+ "Cannot construct a BigUnsigned from a negative number";
+ else
+ initFromPrimitive(x);
+}
+
+// CONVERSION TO PRIMITIVE INTEGERS
+
+/* Template with the same idea as initFromPrimitive. This might be slightly
+ * slower than the previous version with the masks, but it's much shorter and
+ * clearer, which is the library's stated goal. */
+template <class X>
+X BigUnsigned::convertToPrimitive() const {
+ if (len == 0)
+ // The number is zero; return zero.
+ return 0;
+ else if (len == 1) {
+ // The single block might fit in an X. Try the conversion.
+ X x = X(blk[0]);
+ // Make sure the result accurately represents the block.
+ if (Blk(x) == blk[0])
+ // Successful conversion.
+ return x;
+ // Otherwise fall through.
+ }
+ throw "BigUnsigned::to<Primitive>: "
+ "Value is too big to fit in the requested type";
+}
+
+/* Wrap the above in an x >= 0 test to make sure we got a nonnegative result,
+ * not a negative one that happened to convert back into the correct nonnegative
+ * one. (E.g., catch incorrect conversion of 2^31 to the long -2^31.) Again,
+ * separated to avoid a g++ warning. */
+template <class X>
+X BigUnsigned::convertToSignedPrimitive() const {
+ X x = convertToPrimitive<X>();
+ if (x >= 0)
+ return x;
+ else
+ throw "BigUnsigned::to(Primitive): "
+ "Value is too big to fit in the requested type";
}
#endif
Matt McCutchen's Web Site / bigint / bigint.git / blobdiff