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Subject: [Boost-commit] svn:boost r80100 - sandbox/rational
From: dansearles_at_[hidden]
Date: 2012-08-20 18:55:06

Author: mrdans
Date: 2012-08-20 18:55:05 EDT (Mon, 20 Aug 2012)
New Revision: 80100
URL: http://svn.boost.org/trac/boost/changeset/80100

Log:
Initial add for rational.hpp with over/underflow checking
Added:
   sandbox/rational/rational.hpp (contents, props changed)

Added: sandbox/rational/rational.hpp
==============================================================================
--- (empty file)
+++ sandbox/rational/rational.hpp 2012-08-20 18:55:05 EDT (Mon, 20 Aug 2012)
@@ -0,0 +1,992 @@
+// Boost rational.hpp header file ------------------------------------------//
+
+// (C) Copyright Paul Moore 1999. Permission to copy, use, modify, sell and
+// distribute this software is granted provided this copyright notice appears
+// in all copies. This software is provided "as is" without express or
+// implied warranty, and with no claim as to its suitability for any purpose.
+
+// boostinspect:nolicense (don't complain about the lack of a Boost license)
+// (Paul Moore hasn't been in contact for years, so there's no way to change the
+// license.)
+
+// See http://www.boost.org/libs/rational for documentation.
+
+// Credits:
+// Thanks to the boost mailing list in general for useful comments.
+// Particular contributions included:
+// Andrew D Jewell, for reminding me to take care to avoid overflow
+// Ed Brey, for many comments, including picking up on some dreadful typos
+// Stephen Silver contributed the test suite and comments on user-defined
+// IntType
+// Nickolay Mladenov, for the implementation of operator+=
+
+// Revision History
+// 31 Jul 12 Added "CheckForOverflow" template parameter and support for
+// over/underflow checking (new exception: rational_overflow)
+// (Dan Searles)
+// 05 May 12 Reduced use of implicit gcd (Mario Lang)
+// 05 Nov 06 Change rational_cast to not depend on division between different
+// types (Daryle Walker)
+// 04 Nov 06 Off-load GCD and LCM to Boost.Math; add some invariant checks;
+// add std::numeric_limits<> requirement to help GCD (Daryle Walker)
+// 31 Oct 06 Recoded both operator< to use round-to-negative-infinity
+// divisions; the rational-value version now uses continued fraction
+// expansion to avoid overflows, for bug #798357 (Daryle Walker)
+// 20 Oct 06 Fix operator bool_type for CW 8.3 (Joaquín M López Muñoz)
+// 18 Oct 06 Use EXPLICIT_TEMPLATE_TYPE helper macros from Boost.Config
+// (Joaquín M López Muñoz)
+// 27 Dec 05 Add Boolean conversion operator (Daryle Walker)
+// 28 Sep 02 Use _left versions of operators from operators.hpp
+// 05 Jul 01 Recode gcd(), avoiding std::swap (Helmut Zeisel)
+// 03 Mar 01 Workarounds for Intel C++ 5.0 (David Abrahams)
+// 05 Feb 01 Update operator>> to tighten up input syntax
+// 05 Feb 01 Final tidy up of gcd code prior to the new release
+// 27 Jan 01 Recode abs() without relying on abs(IntType)
+// 21 Jan 01 Include Nickolay Mladenov's operator+= algorithm,
+// tidy up a number of areas, use newer features of operators.hpp
+// (reduces space overhead to zero), add operator!,
+// introduce explicit mixed-mode arithmetic operations
+// 12 Jan 01 Include fixes to handle a user-defined IntType better
+// 19 Nov 00 Throw on divide by zero in operator /= (John (EBo) David)
+// 23 Jun 00 Incorporate changes from Mark Rodgers for Borland C++
+// 22 Jun 00 Change _MSC_VER to BOOST_MSVC so other compilers are not
+// affected (Beman Dawes)
+// 6 Mar 00 Fix operator-= normalization, #include <string> (Jens Maurer)
+// 14 Dec 99 Modifications based on comments from the boost list
+// 09 Dec 99 Initial Version (Paul Moore)
+
+#ifndef BOOST_RATIONAL_HPP
+#define BOOST_RATIONAL_HPP
+
+#include <iostream> // for std::istream and std::ostream
+#include <ios> // for std::noskipws
+#include <stdexcept> // for std::domain_error
+#include <string> // for std::string implicit constructor
+#include <boost/operators.hpp> // for boost::addable etc
+#include <cstdlib> // for std::abs
+#include <boost/call_traits.hpp> // for boost::call_traits
+#include <boost/config.hpp> // for BOOST_NO_STDC_NAMESPACE, BOOST_MSVC
+#include <boost/detail/workaround.hpp> // for BOOST_WORKAROUND
+#include <boost/assert.hpp> // for BOOST_ASSERT
+#include <boost/math/common_factor_rt.hpp> // for boost::math::gcd, lcm
+#include <limits> // for std::numeric_limits
+#include <boost/static_assert.hpp> // for BOOST_STATIC_ASSERT
+
+namespace boost {
+
+// This is just a helper function for the overflow checking path.
+// For a given integer type (signed), multiply 2 values into separate 'high'
+// and 'low' variables of the same type.
+template <typename IntType, bool CheckForOverflow>
+void mul2Int(IntType& resHi, IntType& resLo, IntType F1, IntType F2)
+{
+ BOOST_STATIC_ASSERT(!CheckForOverflow || (CheckForOverflow && ::std::numeric_limits<IntType>::is_signed));
+ const IntType zero(0);
+
+ // Operate on positive values, and track sign for final result.
+ // This requires Inttype be signed.
+ bool signNeg = false;
+ if(F1<zero) {
+ F1=~F1; ++F1; signNeg = !signNeg;
+ }
+ if(F2<zero){
+ F2=~F2; ++F2; signNeg = !signNeg;
+ }
+
+ const int halfnumB = sizeof(IntType)*CHAR_BIT/2;
+ const IntType LoHalfMask = (((IntType)(1))<<halfnumB)-(IntType)(1);
+ IntType F1H = (F1>>halfnumB)&LoHalfMask, F1L = F1&LoHalfMask,
+ F2H = (F2>>halfnumB)&LoHalfMask, F2L = F2&LoHalfMask;
+
+ resLo = F1L * F2L;
+
+ IntType Acc = (resLo >> halfnumB) & LoHalfMask;
+ Acc += F1L * F2H;
+ Acc += F1H * F2L;
+
+ resLo = (resLo & LoHalfMask) + ((Acc & LoHalfMask) << halfnumB);
+ Acc = (Acc>>halfnumB) & LoHalfMask;
+ resHi = Acc + F1H * F2H;
+
+ if(signNeg)
+ {
+ resLo = ~resLo;
+ resHi = ~resHi;
+ resLo += 1;
+ if(resLo == 0)
+ {
+ resHi++;
+ }
+ }
+}
+
+// This is just a helper function for the overflow checking path.
+// Add two "high","low" operands to a "high","low" result.
+// Returns true if over/underflow occured ("high","low" sum cannot hold correct result).
+template <typename IntType, bool CheckForOverflow>
+bool add2Int(IntType& resHi, IntType& resLo, IntType F1H, IntType F1L, IntType F2H, IntType F2L)
+{
+ BOOST_STATIC_ASSERT(!CheckForOverflow || (CheckForOverflow && ::std::numeric_limits<IntType>::is_signed));
+ bool overflow = false;
+ const int numBits = sizeof(IntType)*CHAR_BIT;
+ const IntType MSBfMask = (IntType)(((IntType)(1)) << (numBits-1));
+ const IntType zero(0);
+ const IntType one(1);
+
+ // This requires Inttype be signed.
+ if(F1L<zero)
+ {
+ if(F2L<zero)
+ { // Both low parts are negative, 1 will always carry to high part
+ resLo = F1L+F2L;
+ resHi = F1H+F2H+one;
+ }
+ else
+ { // F1L negative, F2L positive
+ F1L &= ~MSBfMask;
+ resLo = F1L+F2L;
+ if(resLo&MSBfMask) resHi = F1H+F2H+one;
+ else resHi = F1H+F2H;
+ resLo += MSBfMask;
+ }
+ }
+ else
+ {
+ if(F2L<zero)
+ { // F1L positive, F2L negative
+ F2L &= ~MSBfMask;
+ resLo = F1L+F2L;
+ if(resLo&MSBfMask) resHi = F1H+F2H+one;
+ else resHi = F1H+F2H;
+ resLo += MSBfMask;
+ }
+ else
+ { // Both low parts are positive, 1 will never carry to high part
+ resLo = F1L+F2L;
+ resHi = F1H+F2H;
+ }
+ }
+ if(((resHi^F1H) & ((~(F1H^F2H))) & MSBfMask))
+ overflow = true;
+ return overflow;
+}
+
+} // namespace boost
+
+// Control whether depreciated GCD and LCM functions are included (default: yes)
+#ifndef BOOST_CONTROL_RATIONAL_HAS_GCD
+#define BOOST_CONTROL_RATIONAL_HAS_GCD 1
+#endif
+
+namespace boost {
+
+#if BOOST_CONTROL_RATIONAL_HAS_GCD
+template <typename IntType>
+IntType gcd(IntType n, IntType m)
+{
+ // Defer to the version in Boost.Math
+ return math::gcd( n, m );
+}
+
+template <typename IntType>
+IntType lcm(IntType n, IntType m)
+{
+ // Defer to the version in Boost.Math
+ return math::lcm( n, m );
+}
+#endif // BOOST_CONTROL_RATIONAL_HAS_GCD
+
+class bad_rational : public std::domain_error
+{
+public:
+ explicit bad_rational() : std::domain_error("bad rational: zero denominator") {}
+};
+
+class rational_overflow : public std::domain_error
+{
+public:
+ explicit rational_overflow() : std::domain_error("rational error: over or underflow") {}
+};
+
+template <typename IntType, bool CheckForOverflow=false>
+class rational;
+
+template <typename IntType, bool CheckForOverflow>
+rational<IntType, CheckForOverflow> abs(const rational<IntType, CheckForOverflow>& r);
+
+template <typename IntType, bool CheckForOverflow>
+class rational :
+ less_than_comparable < rational<IntType, CheckForOverflow>,
+ equality_comparable < rational<IntType, CheckForOverflow>,
+ less_than_comparable2 < rational<IntType, CheckForOverflow>, IntType,
+ equality_comparable2 < rational<IntType, CheckForOverflow>, IntType,
+ addable < rational<IntType, CheckForOverflow>,
+ subtractable < rational<IntType, CheckForOverflow>,
+ multipliable < rational<IntType, CheckForOverflow>,
+ dividable < rational<IntType, CheckForOverflow>,
+ addable2 < rational<IntType, CheckForOverflow>, IntType,
+ subtractable2 < rational<IntType, CheckForOverflow>, IntType,
+ subtractable2_left < rational<IntType, CheckForOverflow>, IntType,
+ multipliable2 < rational<IntType, CheckForOverflow>, IntType,
+ dividable2 < rational<IntType, CheckForOverflow>, IntType,
+ dividable2_left < rational<IntType, CheckForOverflow>, IntType,
+ incrementable < rational<IntType, CheckForOverflow>,
+ decrementable < rational<IntType, CheckForOverflow>
+ > > > > > > > > > > > > > > > >
+{
+ // Class-wide pre-conditions
+ BOOST_STATIC_ASSERT( ::std::numeric_limits<IntType>::is_specialized );
+
+ // Checking for overflow requires IntType be signed.
+ BOOST_STATIC_ASSERT(!CheckForOverflow || (CheckForOverflow && std::numeric_limits<IntType>::is_signed));
+
+ // Helper types
+ typedef typename boost::call_traits<IntType>::param_type param_type;
+
+ struct helper { IntType parts[2]; };
+ typedef IntType (helper::* bool_type)[2];
+
+public:
+ typedef IntType int_type;
+ rational() : num(0), den(1) {}
+ rational(param_type n) : num(n), den(1) {}
+ rational(param_type n, param_type d) : num(n), den(d) {normalize();}
+
+ // Default copy constructor and assignment are fine
+
+ // Add assignment from IntType
+ rational& operator=(param_type i) { num = i; den = 1; return *this; }
+
+ // Assign in place
+ rational& assign(param_type n, param_type d);
+
+ // Access to representation
+ IntType numerator() const { return num; }
+ IntType denominator() const { return den; }
+
+ // Arithmetic assignment operators
+ rational& operator+= (const rational& r);
+ rational& operator-= (const rational& r);
+ rational& operator*= (const rational& r);
+ rational& operator/= (const rational& r);
+
+ rational& operator+= (param_type i);
+ rational& operator-= (param_type i);
+ rational& operator*= (param_type i);
+ rational& operator/= (param_type i);
+
+ // Increment and decrement
+ const rational& operator++();
+ const rational& operator--();
+
+ // Operator not
+ bool operator!() const { return !num; }
+
+ // Boolean conversion
+
+#if BOOST_WORKAROUND(__MWERKS__,<=0x3003)
+ // The "ISO C++ Template Parser" option in CW 8.3 chokes on the
+ // following, hence we selectively disable that option for the
+ // offending memfun.
+#pragma parse_mfunc_templ off
+#endif
+
+ operator bool_type() const { return operator !() ? 0 : &helper::parts; }
+
+#if BOOST_WORKAROUND(__MWERKS__,<=0x3003)
+#pragma parse_mfunc_templ reset
+#endif
+
+ // Comparison operators
+ bool operator< (const rational& r) const;
+ bool operator== (const rational& r) const;
+
+ bool operator< (param_type i) const;
+ bool operator> (param_type i) const;
+ bool operator== (param_type i) const;
+
+private:
+ // Implementation - numerator and denominator (normalized).
+ // Other possibilities - separate whole-part, or sign, fields?
+ IntType num;
+ IntType den;
+
+ // Representation note: Fractions are kept in normalized form at all
+ // times. Normalized form is defined as gcd(num,den) == 1 and den > 0.
+ // In particular, note that the implementation of abs() below relies
+ // on den always being positive.
+ bool test_invariant() const;
+ void normalize();
+};
+
+// Assign in place
+template <typename IntType, bool CheckForOverflow>
+inline rational<IntType, CheckForOverflow>& rational<IntType, CheckForOverflow>::assign(param_type n, param_type d)
+{
+ num = n;
+ den = d;
+ normalize();
+ return *this;
+}
+
+// Unary plus and minus
+template <typename IntType, bool CheckForOverflow>
+inline rational<IntType, CheckForOverflow> operator+ (const rational<IntType, CheckForOverflow>& r)
+{
+ return r;
+}
+
+template <typename IntType, bool CheckForOverflow>
+inline rational<IntType, CheckForOverflow> operator- (const rational<IntType, CheckForOverflow>& r)
+{
+ IntType negnumer = ~r.numerator(); ++negnumer;
+ if(CheckForOverflow)
+ {
+ if(negnumer && (r.numerator() == negnumer))
+ throw rational_overflow();
+ }
+ return rational<IntType, CheckForOverflow>(negnumer, r.denominator());
+}
+
+// Arithmetic assignment operators
+template <typename IntType, bool CheckForOverflow>
+rational<IntType, CheckForOverflow>& rational<IntType, CheckForOverflow>::operator+= (const rational<IntType, CheckForOverflow>& r)
+{
+ if(CheckForOverflow)
+ {
+ const int numBits = sizeof(IntType)*CHAR_BIT;
+ const IntType zero(0);
+ const IntType one(1);
+ const IntType neg1(-1);
+ IntType part1H,part1L,part2H,part2L,newnumH,T;
+
+ // Protect against self-modification
+ IntType r_num = r.num;
+ IntType r_den = r.den;
+ IntType r_den_g = r.den;
+
+ IntType g = math::gcd(den, r_den);
+
+ if(g != one)
+ {
+ den /= g;
+ r_den_g /= g;
+ }
+
+ mul2Int<IntType, CheckForOverflow>(part1H,part1L, num, r_den_g);
+ mul2Int<IntType, CheckForOverflow>(part2H,part2L, r_num, den);
+ bool ovfl = add2Int<IntType, CheckForOverflow>(newnumH, num,part1H,part1L,part2H,part2L);
+ T = num>>(numBits-1);
+ if(newnumH!=T)
+ throw rational_overflow();
+
+ g = math::gcd(num, g);
+ if(g!=one)
+ {
+ num /= g;
+ r_den /= g;
+ }
+
+ mul2Int<IntType, CheckForOverflow>(part1H,den, den, r_den);
+ if((part1H!=zero) || (den<zero))
+ throw rational_overflow();
+ }
+ else
+ {
+ // This calculation avoids overflow, and minimises the number of expensive
+ // calculations. Thanks to Nickolay Mladenov for this algorithm.
+ //
+ // Proof:
+ // We have to compute a/b + c/d, where gcd(a,b)=1 and gcd(b,c)=1.
+ // Let g = gcd(b,d), and b = b1*g, d=d1*g. Then gcd(b1,d1)=1
+ //
+ // The result is (a*d1 + c*b1) / (b1*d1*g).
+ // Now we have to normalize this ratio.
+ // Let's assume h | gcd((a*d1 + c*b1), (b1*d1*g)), and h > 1
+ // If h | b1 then gcd(h,d1)=1 and hence h|(a*d1+c*b1) => h|a.
+ // But since gcd(a,b1)=1 we have h=1.
+ // Similarly h|d1 leads to h=1.
+ // So we have that h | gcd((a*d1 + c*b1) , (b1*d1*g)) => h|g
+ // Finally we have gcd((a*d1 + c*b1), (b1*d1*g)) = gcd((a*d1 + c*b1), g)
+ // Which proves that instead of normalizing the result, it is better to
+ // divide num and den by gcd((a*d1 + c*b1), g)
+
+ // Protect against self-modification
+ IntType r_num = r.num;
+ IntType r_den = r.den;
+
+ IntType g = math::gcd(den, r_den);
+ den /= g; // = b1 from the calculations above
+ num = num * (r_den / g) + r_num * den;
+ g = math::gcd(num, g);
+ num /= g;
+ den *= r_den/g;
+ }
+
+ return *this;
+}
+
+template <typename IntType, bool CheckForOverflow>
+rational<IntType, CheckForOverflow>& rational<IntType, CheckForOverflow>::operator-= (const rational<IntType, CheckForOverflow>& r)
+{
+ if(CheckForOverflow)
+ {
+ if((num==r.num) && (den==r.den)) {
+ num = IntType(0);
+ den = IntType(1);
+ return *this;
+ }
+
+ // Negate the denominator (which is safe), and use constructor 'normalize' to check for overflow.
+ IntType negrden = ~r.den; ++negrden;
+ rational<IntType, CheckForOverflow> negOperand(r.num, negrden);
+ return operator+= (negOperand);
+ }
+ else
+ {
+ // Protect against self-modification
+ IntType r_num = r.num;
+ IntType r_den = r.den;
+
+ // This calculation avoids overflow, and minimises the number of expensive
+ // calculations. It corresponds exactly to the += case above
+ IntType g = math::gcd(den, r_den);
+ den /= g;
+ num = num * (r_den / g) - r_num * den;
+ g = math::gcd(num, g);
+ num /= g;
+ den *= r_den/g;
+
+ return *this;
+ }
+}
+
+template <typename IntType, bool CheckForOverflow>
+rational<IntType, CheckForOverflow>& rational<IntType, CheckForOverflow>::operator*= (const rational<IntType, CheckForOverflow>& r)
+{
+ // Protect against self-modification
+ IntType r_num = r.num;
+ IntType r_den = r.den;
+
+ // Avoid overflow and preserve normalization
+ IntType gcd1 = math::gcd(num, r_den);
+ IntType gcd2 = math::gcd(r_num, den);
+
+ if(CheckForOverflow)
+ {
+ const int numBits = sizeof(IntType)*CHAR_BIT;
+ const IntType one = IntType(1);
+ const IntType zero = IntType(0);
+ IntType num_gcd1=num, den_gcd2=den, signbits;
+ if(gcd1!=one) {
+ num_gcd1 /= gcd1;
+ r_den /= gcd1;
+ }
+ if(gcd2!=one) {
+ den_gcd2 /= gcd2;
+ r_num /= gcd2;
+ }
+ mul2Int<IntType, CheckForOverflow>(signbits,num, num_gcd1, r_num);
+ if(IntType(num>>(numBits-1)) != signbits)
+ throw rational_overflow();
+
+ mul2Int<IntType, CheckForOverflow>(signbits,den, den_gcd2, r_den);
+ if((signbits!=zero) || (den<zero))
+ throw rational_overflow();
+ }
+ else
+ {
+ num = (num/gcd1) * (r_num/gcd2);
+ den = (den/gcd2) * (r_den/gcd1);
+ }
+ return *this;
+}
+
+template <typename IntType, bool CheckForOverflow>
+rational<IntType, CheckForOverflow>& rational<IntType, CheckForOverflow>::operator/= (const rational<IntType, CheckForOverflow>& r)
+{
+ // Protect against self-modification
+ IntType r_num = r.num;
+ IntType r_den = r.den;
+
+ // Avoid repeated construction
+ const IntType zero(0);
+
+ // Trap division by zero
+ if (r_num == zero)
+ throw bad_rational();
+ if (num == zero)
+ return *this;
+
+ // Avoid overflow and preserve normalization
+ IntType gcd1 = math::gcd(num, r_num);
+ IntType gcd2 = math::gcd(r_den, den);
+
+ if(CheckForOverflow)
+ {
+ const int numBits = sizeof(IntType)*CHAR_BIT;
+ const IntType one = IntType(1);
+ IntType num_gcd1=num, den_gcd2=den, signbits;
+ if(gcd1!=one) {
+ num_gcd1 /= gcd1;
+ r_num /= gcd1;
+ }
+ if(gcd2!=one) {
+ den_gcd2 /= gcd2;
+ r_den /= gcd2;
+ }
+ mul2Int<IntType, CheckForOverflow>(signbits,num, num_gcd1, r_den);
+ if(IntType(num>>(numBits-1)) != signbits)
+ throw rational_overflow();
+
+ mul2Int<IntType, CheckForOverflow>(signbits,den, den_gcd2, r_num);
+ if(IntType(den>>(numBits-1)) != signbits)
+ throw rational_overflow();
+
+ if (den < zero)
+ {
+ IntType negden = ~den; ++negden;
+ IntType negnum = ~num; ++negnum;
+ if(den == negden) // den never zero here
+ throw rational_overflow();
+ if(num && (num == negnum))
+ throw rational_overflow();
+
+ num = negnum;
+ den = negden;
+ }
+ }
+ else
+ {
+ num = (num/gcd1) * (r_den/gcd2);
+ den = (den/gcd2) * (r_num/gcd1);
+
+ if (den < zero) {
+ num = -num;
+ den = -den;
+ }
+ }
+ return *this;
+}
+
+// Mixed-mode operators
+template <typename IntType, bool CheckForOverflow>
+inline rational<IntType, CheckForOverflow>&
+rational<IntType, CheckForOverflow>::operator*= (param_type i)
+{
+ if(CheckForOverflow)
+ return operator*= (rational<IntType, CheckForOverflow>(i));
+
+ // Avoid overflow and preserve normalization
+ IntType gcd = math::gcd(i, den);
+ num *= i / gcd;
+ den /= gcd;
+
+ return *this;
+}
+
+template <typename IntType, bool CheckForOverflow>
+inline rational<IntType, CheckForOverflow>&
+rational<IntType, CheckForOverflow>::operator/= (param_type i)
+{
+ if(CheckForOverflow)
+ return operator/= (rational<IntType, CheckForOverflow>(i));
+
+ // Avoid repeated construction
+ IntType const zero(0);
+
+ if (i == zero) throw bad_rational();
+ if (num == zero) return *this;
+
+ // Avoid overflow and preserve normalization
+ IntType const gcd = math::gcd(num, i);
+ num /= gcd;
+ den *= i / gcd;
+
+ if (den < zero) {
+ num = -num;
+ den = -den;
+ }
+
+ return *this;
+}
+
+template <typename IntType, bool CheckForOverflow>
+inline rational<IntType, CheckForOverflow>&
+rational<IntType, CheckForOverflow>::operator+= (param_type i)
+{
+ if(CheckForOverflow)
+ return operator+= (rational<IntType, CheckForOverflow>(i));
+
+ num += i * den;
+ return *this;
+}
+
+template <typename IntType, bool CheckForOverflow>
+inline rational<IntType, CheckForOverflow>&
+rational<IntType, CheckForOverflow>::operator-= (param_type i)
+{
+ if(CheckForOverflow)
+ return operator-= (rational<IntType, CheckForOverflow>(i));
+
+ num -= i * den;
+ return *this;
+}
+
+// Increment and decrement
+template <typename IntType, bool CheckForOverflow>
+inline const rational<IntType, CheckForOverflow>& rational<IntType, CheckForOverflow>::operator++()
+{
+ if(CheckForOverflow)
+ {
+ const IntType zero( 0 );
+ if((num>zero) && (IntType(num + den) < zero))
+ throw rational_overflow();
+ }
+
+ // This can never denormalise the fraction
+ num += den;
+ return *this;
+}
+
+template <typename IntType, bool CheckForOverflow>
+inline const rational<IntType, CheckForOverflow>& rational<IntType, CheckForOverflow>::operator--()
+{
+ if(CheckForOverflow)
+ {
+ const IntType zero( 0 );
+ if((num<zero) && (IntType(num - den) >= zero))
+ throw rational_overflow();
+ }
+
+ // This can never denormalise the fraction
+ num -= den;
+ return *this;
+}
+
+// Comparison operators
+template <typename IntType, bool CheckForOverflow>
+bool rational<IntType, CheckForOverflow>::operator< (const rational<IntType, CheckForOverflow>& r) const
+{
+ // Avoid repeated construction
+ int_type const zero( 0 );
+
+ if(CheckForOverflow)
+ {
+ IntType ProdLeftH, ProdLeftL, ProdRghtH, ProdRghtL;
+ mul2Int<IntType, CheckForOverflow>(ProdLeftH, ProdLeftL, num, r.den);
+ mul2Int<IntType, CheckForOverflow>(ProdRghtH, ProdRghtL, r.num, den);
+ if(ProdLeftH < ProdRghtH)
+ return true;
+ else if(ProdLeftH == ProdRghtH)
+ {
+ const int numBits = sizeof(IntType)*CHAR_BIT;
+ const IntType MSBfMask = (IntType)(((IntType)(1)) << (numBits-1));
+ ProdLeftL ^= MSBfMask; // Convert to signed
+ ProdRghtL ^= MSBfMask; // Convert to signed
+ return ProdLeftL < ProdRghtL;
+ }
+ else
+ return false;
+ }
+ else
+ {
+ // This should really be a class-wide invariant. The reason for these
+ // checks is that for 2's complement systems, INT_MIN has no corresponding
+ // positive, so negating it during normalization keeps it INT_MIN, which
+ // is bad for later calculations that assume a positive denominator.
+ BOOST_ASSERT( this->den > zero );
+ BOOST_ASSERT( r.den > zero );
+
+ // Determine relative order by expanding each value to its simple continued
+ // fraction representation using the Euclidian GCD algorithm.
+ struct { int_type n, d, q, r; } ts = { this->num, this->den, this->num /
+ this->den, this->num % this->den }, rs = { r.num, r.den, r.num / r.den,
+ r.num % r.den };
+ unsigned reverse = 0u;
+
+ // Normalize negative moduli by repeatedly adding the (positive) denominator
+ // and decrementing the quotient. Later cycles should have all positive
+ // values, so this only has to be done for the first cycle. (The rules of
+ // C++ require a nonnegative quotient & remainder for a nonnegative dividend
+ // & positive divisor.)
+ while ( ts.r < zero ) { ts.r += ts.d; --ts.q; }
+ while ( rs.r < zero ) { rs.r += rs.d; --rs.q; }
+
+ // Loop through and compare each variable's continued-fraction components
+ while ( true )
+ {
+ // The quotients of the current cycle are the continued-fraction
+ // components. Comparing two c.f. is comparing their sequences,
+ // stopping at the first difference.
+ if ( ts.q != rs.q )
+ {
+ // Since reciprocation changes the relative order of two variables,
+ // and c.f. use reciprocals, the less/greater-than test reverses
+ // after each index. (Start w/ non-reversed @ whole-number place.)
+ return reverse ? ts.q > rs.q : ts.q < rs.q;
+ }
+
+ // Prepare the next cycle
+ reverse ^= 1u;
+
+ if ( (ts.r == zero) || (rs.r == zero) )
+ {
+ // At least one variable's c.f. expansion has ended
+ break;
+ }
+
+ ts.n = ts.d; ts.d = ts.r;
+ ts.q = ts.n / ts.d; ts.r = ts.n % ts.d;
+ rs.n = rs.d; rs.d = rs.r;
+ rs.q = rs.n / rs.d; rs.r = rs.n % rs.d;
+ }
+
+ // Compare infinity-valued components for otherwise equal sequences
+ if ( ts.r == rs.r )
+ {
+ // Both remainders are zero, so the next (and subsequent) c.f.
+ // components for both sequences are infinity. Therefore, the sequences
+ // and their corresponding values are equal.
+ return false;
+ }
+ else
+ {
+ #ifdef BOOST_MSVC
+ #pragma warning(push)
+ #pragma warning(disable:4800)
+ #endif
+ // Exactly one of the remainders is zero, so all following c.f.
+ // components of that variable are infinity, while the other variable
+ // has a finite next c.f. component. So that other variable has the
+ // lesser value (modulo the reversal flag!).
+ return ( ts.r != zero ) != static_cast<bool>( reverse );
+ #ifdef BOOST_MSVC
+ #pragma warning(pop)
+ #endif
+ }
+ }
+}
+
+template <typename IntType, bool CheckForOverflow>
+bool rational<IntType, CheckForOverflow>::operator< (param_type i) const
+{
+ if(CheckForOverflow)
+ {
+ IntType ProdLeftH, ProdLeftL, ProdRghtH, ProdRghtL;
+ mul2Int<IntType, CheckForOverflow>(ProdLeftH, ProdLeftL, num, IntType(1));
+ mul2Int<IntType, CheckForOverflow>(ProdRghtH, ProdRghtL, i, den);
+ if(ProdLeftH < ProdRghtH)
+ return true;
+ else if(ProdLeftH == ProdRghtH)
+ {
+ const int numBits = sizeof(IntType)*CHAR_BIT;
+ const IntType MSBfMask = (IntType)(((IntType)(1)) << (numBits-1));
+ ProdLeftL ^= MSBfMask; // Convert to signed
+ ProdRghtL ^= MSBfMask; // Convert to signed
+ return ProdLeftL < ProdRghtL;
+ }
+ else
+ return false;
+ }
+ else
+ {
+ // Avoid repeated construction
+ int_type const zero( 0 );
+
+ // Break value into mixed-fraction form, w/ always-nonnegative remainder
+ BOOST_ASSERT( this->den > zero );
+ int_type q = this->num / this->den, r = this->num % this->den;
+ while ( r < zero ) { r += this->den; --q; }
+
+ // Compare with just the quotient, since the remainder always bumps the
+ // value up. [Since q = floor(n/d), and if n/d < i then q < i, if n/d == i
+ // then q == i, if n/d == i + r/d then q == i, and if n/d >= i + 1 then
+ // q >= i + 1 > i; therefore n/d < i iff q < i.]
+ return q < i;
+ }
+}
+
+template <typename IntType, bool CheckForOverflow>
+bool rational<IntType, CheckForOverflow>::operator> (param_type i) const
+{
+ return operator==(i)? false: !operator<(i);
+}
+
+template <typename IntType, bool CheckForOverflow>
+inline bool rational<IntType, CheckForOverflow>::operator== (const rational<IntType, CheckForOverflow>& r) const
+{
+ return ((num == r.num) && (den == r.den));
+}
+
+template <typename IntType, bool CheckForOverflow>
+inline bool rational<IntType, CheckForOverflow>::operator== (param_type i) const
+{
+ return ((den == IntType(1)) && (num == i));
+}
+
+// Invariant check
+template <typename IntType, bool CheckForOverflow>
+inline bool rational<IntType, CheckForOverflow>::test_invariant() const
+{
+ return ( this->den > int_type(0) ) && ( math::gcd(this->num, this->den) ==
+ int_type(1) );
+}
+
+// Normalisation
+template <typename IntType, bool CheckForOverflow>
+void rational<IntType, CheckForOverflow>::normalize()
+{
+ // Avoid repeated construction
+ const IntType zero(0);
+
+ if (den == zero)
+ throw bad_rational();
+
+ // Handle the case of zero separately, to avoid division by zero
+ const IntType one(1);
+ if (num == zero) {
+ den = one;
+ return;
+ }
+
+ IntType g = math::gcd(num, den);
+
+ if(g != one)
+ {
+ num /= g;
+ den /= g;
+ }
+
+ // Ensure that the denominator is positive
+ if (den < zero)
+ {
+ IntType negden = ~den; ++negden;
+ IntType negnum = ~num; ++negnum;
+ if(CheckForOverflow)
+ {
+ if(den == negden) // den never zero here
+ throw rational_overflow();
+ if(num == negnum) // num never zero here
+ throw rational_overflow();
+ }
+ den = negden;
+ num = negnum;
+ }
+
+ BOOST_ASSERT( this->test_invariant() );
+}
+
+namespace detail {
+
+ // A utility class to reset the format flags for an istream at end
+ // of scope, even in case of exceptions
+ struct resetter {
+ resetter(std::istream& is) : is_(is), f_(is.flags()) {}
+ ~resetter() { is_.flags(f_); }
+ std::istream& is_;
+ std::istream::fmtflags f_; // old GNU c++ lib has no ios_base
+ };
+
+}
+
+// Input and output
+template <typename IntType, bool CheckForOverflow>
+std::istream& operator>> (std::istream& is, rational<IntType, CheckForOverflow>& r)
+{
+ IntType n = IntType(0), d = IntType(1);
+ char c = 0;
+ detail::resetter sentry(is);
+
+ is >> n;
+ c = is.get();
+
+ if (c != '/')
+ is.clear(std::istream::badbit); // old GNU c++ lib has no ios_base
+
+#if !defined(__GNUC__) || (defined(__GNUC__) && (__GNUC__ >= 3)) || defined __SGI_STL_PORT
+ is >> std::noskipws;
+#else
+ is.unsetf(ios::skipws); // compiles, but seems to have no effect.
+#endif
+ is >> d;
+
+ if (is)
+ r.assign(n, d);
+
+ return is;
+}
+
+// Add manipulators for output format?
+template <typename IntType, bool CheckForOverflow>
+std::ostream& operator<< (std::ostream& os, const rational<IntType, CheckForOverflow>& r)
+{
+ os << r.numerator() << '/' << r.denominator();
+ return os;
+}
+
+// Create overloads for signed char, so numbers will get printed, instead of characters.
+std::ostream& operator<< (std::ostream& os, const rational<signed char, true>& r)
+{
+ os << (int)r.numerator() << '/' << (int)r.denominator();
+ return os;
+}
+
+std::ostream& operator<< (std::ostream& os, const rational<signed char, false>& r)
+{
+ os << (int)r.numerator() << '/' << (int)r.denominator();
+ return os;
+}
+
+
+// Type conversion
+template <typename T, typename IntType, bool CheckForOverflow>
+inline T rational_cast(
+ const rational<IntType, CheckForOverflow>& src BOOST_APPEND_EXPLICIT_TEMPLATE_TYPE(T))
+{
+ return static_cast<T>(src.numerator())/static_cast<T>(src.denominator());
+}
+
+// Do not use any abs() defined on IntType - it isn't worth it, given the
+// difficulties involved (Koenig lookup required, there may not *be* an abs()
+// defined, etc etc).
+template <typename IntType, bool CheckForOverflow>
+inline rational<IntType, CheckForOverflow> abs(const rational<IntType, CheckForOverflow>& r)
+{
+ if(CheckForOverflow)
+ {
+ const IntType zero(0);
+
+ if (r.numerator() >= zero)
+ return r;
+ else
+ {
+ IntType negnumer = ~r.numerator(); ++negnumer;
+ if(r.numerator() == negnumer) // numer is never zero here
+ throw rational_overflow();
+
+ return -r;
+ }
+ }
+ else
+ return r.numerator() >= IntType(0)? r: -r;
+}
+
+typedef rational<signed char,true> RatSCharwOvCk;
+typedef rational<signed char,false> RatSChar;
+
+typedef rational<short,true> RatSShortwOvCk;
+typedef rational<short,false> RatShort;
+
+typedef rational<int,true> RatSIntwOvCk;
+typedef rational<int,false> RatSInt;
+
+typedef rational<long long,true> RatSLLwOvCk;
+typedef rational<long long,false> RatSLL;
+
+
+} // namespace boost
+
+
+#endif // BOOST_RATIONAL_HPP
+

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