X-Git-Url: https://mattmccutchen.net/bigint/bigint.git/blobdiff_plain/4efbb07622a0aa83db4fe05ca8c17aca406ed928..0551c03b5862aafe7f5f88cf282ebf96621c6c80:/BigUnsigned.hh diff --git a/BigUnsigned.hh b/BigUnsigned.hh index 72513af..61fcb90 100644 --- a/BigUnsigned.hh +++ b/BigUnsigned.hh @@ -1,6 +1,5 @@ /* * Matt McCutchen's Big Integer Library -* http://mysite.verizon.net/mccutchen/bigint/ */ #ifndef BIGUNSIGNED @@ -104,53 +103,94 @@ class BigUnsigned : protected NumberlikeArray { // Compares this to x like Perl's <=> CmpRes compareTo(const BigUnsigned &x) const; // Normal comparison operators - NumberlikeArray::operator ==; // (NlA) The body used to be `{ return compareTo(x) == equal; }'. For performance reasons we use NumberlikeArray code that only worries about (in)equality and doesn't waste time determining which is bigger - NumberlikeArray::operator !=; // (NlA) Ditto. + // Bug fixed 2006.04.24: Only we, not the user, can pass a BigUnsigned off as a + // NumberlikeArray, so we have to wrap == and !=. + bool operator ==(const BigUnsigned &x) const { + return NumberlikeArray::operator ==(x); + } + bool operator !=(const BigUnsigned &x) const { + return NumberlikeArray::operator !=(x); + } bool operator < (const BigUnsigned &x) const { return compareTo(x) == less ; } bool operator <=(const BigUnsigned &x) const { return compareTo(x) != greater; } bool operator >=(const BigUnsigned &x) const { return compareTo(x) != less ; } bool operator > (const BigUnsigned &x) const { return compareTo(x) == greater; } + + /* + * BigUnsigned and BigInteger both provide three kinds of operators. + * Here ``big-integer'' refers to BigInteger or BigUnsigned. + * + * (1) Overloaded ``return-by-value'' operators: + * +, -, *, /, %, unary -. + * Big-integer code using these operators looks identical to + * code using the primitive integer types. These operators take + * one or two big-integer inputs and return a big-integer result, + * which can then be assigned to a BigInteger variable or used + * in an expression. Example: + * BigInteger a(1), b = 1; + * BigInteger c = a + b; + * + * (2) Overloaded assignment operators: + * +=, -=, *=, /=, %=, &=, |=, ^=, ++, --, flipSign. + * Again, these are used on big integers just like on ints. + * They take one writable big integer that both provides an + * operand and receives a result. The first eight also take + * a second read-only operand. Example: + * BigInteger a(1), b(1); + * a += b; + * + * (3) ``Put-here'' operations: `add', `subtract', etc. + * Using a return-by-value or assignment operator generally involves + * copy constructions and/or assignments. The ``put-here'' operations + * require none, but they are more of a hassle to use. Most take two + * read-only operands and save the result in the calling object `*this', + * whose previous value is ignored. `divideWithRemainder' is an exception. + * <<< NOTE >>>: Put-here operations do not return a value: they don't need to!! + * Examples: + * BigInteger a(43), b(7), c, d; + * c = a + b; // Now c == 50. + * c.add(a, b); // Same effect but without the two bulk-copies. + * c.divideWithRemainder(b, d); // 50 / 7; now d == 7 (quotient) and c == 1 (remainder). + * a.add(a, b); // ``Aliased'' calls now do the right thing using a + * // temporary copy, but see note on divideWithRemainder. + */ // PUT-HERE OPERATIONS - /* These store the result of the operation on the arguments into this. - * a.add(b, c) is equivalent to, but faster than, a = b + c. - * Calls like a.operation(a, b) are unsafe and not allowed. */ public: - // Easy 3 - void add (const BigUnsigned &a, const BigUnsigned &b); // Addition - void subtract (const BigUnsigned &a, const BigUnsigned &b); // Subtraction - void multiply (const BigUnsigned &a, const BigUnsigned &b); // Multiplication + /* These 3: Two read-only operands as arguments. Result left in *this. */ + void add(const BigUnsigned &a, const BigUnsigned &b); // Addition + void subtract(const BigUnsigned &a, const BigUnsigned &b); // Subtraction + void multiply(const BigUnsigned &a, const BigUnsigned &b); // Multiplication /* Divisive stuff * `a.divideWithRemainder(b, q)' is like `q = a / b, a %= b'. * Semantics similar to Donald E. Knuth's are used for / and %, * and these differ from the semantics of primitive-type * / and % under division by zero. * Look in `BigUnsigned.cc' for details. + * `a.divideWithRemainder(b, a)' causes an exception: it doesn't make + * sense to write quotient and remainder into the same variable. */ void divideWithRemainder(const BigUnsigned &b, BigUnsigned &q); void divide(const BigUnsigned &a, const BigUnsigned &b) { - // Division, deprecated and provided for compatibility BigUnsigned a2(a); a2.divideWithRemainder(b, *this); // quotient now in *this // don't care about remainder left in a2 } void modulo(const BigUnsigned &a, const BigUnsigned &b) { - // Modular reduction, deprecated and provided for compatibility *this = a; BigUnsigned q; divideWithRemainder(b, q); // remainder now in *this // don't care about quotient left in q } - // Bitwise - void bitAnd (const BigUnsigned &a, const BigUnsigned &b); // Bitwise AND - void bitOr (const BigUnsigned &a, const BigUnsigned &b); // Bitwise OR - void bitXor (const BigUnsigned &a, const BigUnsigned &b); // Bitwise XOR - - // These functions are declared but not defined. (Sorry.) - // Trying to call either will result in a link-time error. - void bitShiftLeft (const BigUnsigned &a, unsigned int b); // Bitwise left shift + // Bitwise operations. Result left in *this. + // These are not provided for BigIntegers; I think that using them on BigIntegers + // will discard the sign first. + void bitAnd(const BigUnsigned &a, const BigUnsigned &b); // Bitwise AND + void bitOr(const BigUnsigned &a, const BigUnsigned &b); // Bitwise OR + void bitXor(const BigUnsigned &a, const BigUnsigned &b); // Bitwise XOR + void bitShiftLeft(const BigUnsigned &a, unsigned int b); // Bitwise left shift void bitShiftRight(const BigUnsigned &a, unsigned int b); // Bitwise right shift // NORMAL OPERATORS @@ -165,6 +205,11 @@ class BigUnsigned : protected NumberlikeArray { BigUnsigned operator &(const BigUnsigned &x) const; // Bitwise AND BigUnsigned operator |(const BigUnsigned &x) const; // Bitwise OR BigUnsigned operator ^(const BigUnsigned &x) const; // Bitwise XOR + BigUnsigned operator <<(unsigned int b) const; // Bitwise left shift + BigUnsigned operator >>(unsigned int b) const; // Bitwise right shift + // Additional operators in an attempt to avoid overloading tangles. + BigUnsigned operator <<(int b) const; + BigUnsigned operator >>(int b) const; // ASSIGNMENT OPERATORS // These perform the operation on this and x, storing the result into this. @@ -177,6 +222,11 @@ class BigUnsigned : protected NumberlikeArray { void operator &=(const BigUnsigned &x); // Bitwise AND void operator |=(const BigUnsigned &x); // Bitwise OR void operator ^=(const BigUnsigned &x); // Bitwise XOR + void operator <<=(unsigned int b); // Bitwise left shift + void operator >>=(unsigned int b); // Bitwise right shift + // Additional operators in an attempt to avoid overloading tangles. + void operator <<=(int b); + void operator >>=(int b); // INCREMENT/DECREMENT OPERATORS // These increase or decrease the number by 1. To discourage side effects, @@ -235,22 +285,44 @@ inline BigUnsigned BigUnsigned::operator ^(const BigUnsigned &x) const { ans.bitXor(*this, x); return ans; } +inline BigUnsigned BigUnsigned::operator <<(unsigned int b) const { + BigUnsigned ans; + ans.bitShiftLeft(*this, b); + return ans; +} +inline BigUnsigned BigUnsigned::operator >>(unsigned 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 supported"; + return *this << (unsigned int)(b); +} +inline BigUnsigned BigUnsigned::operator >>(int b) const { + if (b < 0) + throw "BigUnsigned::operator >>(int): Negative shift amounts are not supported"; + return *this >> (unsigned int)(b); +} -// ASSIGNMENT OPERATORS -// These create a copy of this, then invoke the appropriate -// put-here operation on this, passing the copy and x. -// Exception: those updated for divideWithRemainder. +/* + * ASSIGNMENT OPERATORS + * + * Now the responsibility for making a temporary copy if necessary + * belongs to the put-here operations. I made this change on 2007.02.13 after + * Boris Dessy pointed out that the old implementation handled calls like + * "a *= a" badly: it translated them to essentially "a.multiply(aCopy, a)", + * which threw an exception. + */ inline void BigUnsigned::operator +=(const BigUnsigned &x) { - BigUnsigned thisCopy(*this); - add(thisCopy, x); + add(*this, x); } inline void BigUnsigned::operator -=(const BigUnsigned &x) { - BigUnsigned thisCopy(*this); - subtract(thisCopy, x); + subtract(*this, x); } inline void BigUnsigned::operator *=(const BigUnsigned &x) { - BigUnsigned thisCopy(*this); - multiply(thisCopy, x); + multiply(*this, x); } inline void BigUnsigned::operator /=(const BigUnsigned &x) { // Updated for divideWithRemainder @@ -267,16 +339,29 @@ inline void BigUnsigned::operator %=(const BigUnsigned &x) { // don't care about quotient left in q } inline void BigUnsigned::operator &=(const BigUnsigned &x) { - BigUnsigned thisCopy(*this); - bitAnd(thisCopy, x); + bitAnd(*this, x); } inline void BigUnsigned::operator |=(const BigUnsigned &x) { - BigUnsigned thisCopy(*this); - bitOr(thisCopy, x); + bitOr(*this, x); } inline void BigUnsigned::operator ^=(const BigUnsigned &x) { - BigUnsigned thisCopy(*this); - bitXor(thisCopy, x); + bitXor(*this, x); +} +inline void BigUnsigned::operator <<=(unsigned int b) { + bitShiftLeft(*this, b); +} +inline void BigUnsigned::operator >>=(unsigned 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); +} +inline void BigUnsigned::operator >>=(int b) { + if (b < 0) + throw "BigUnsigned::operator >>=(int): Negative shift amounts are not supported"; + *this >>= (unsigned int)(b); } #endif