351 lines
11 KiB
C++
351 lines
11 KiB
C++
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/*=============================================================================
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Copyright (c) 2001-2019 Joel de Guzman
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Copyright (c) 2001-2011 Hartmut Kaiser
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http://spirit.sourceforge.net/
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Distributed under the Boost Software License, Version 1.0. (See accompanying
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file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
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=============================================================================*/
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#ifndef BOOST_SPIRIT_QI_NUMERIC_DETAIL_REAL_IMPL_HPP
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#define BOOST_SPIRIT_QI_NUMERIC_DETAIL_REAL_IMPL_HPP
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#if defined(_MSC_VER)
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#pragma once
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#endif
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#include <cmath>
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#include <boost/limits.hpp>
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#include <boost/type_traits/is_same.hpp>
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#include <boost/spirit/home/support/unused.hpp>
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#include <boost/spirit/home/qi/detail/attributes.hpp>
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#include <boost/spirit/home/support/detail/pow10.hpp>
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#include <boost/integer.hpp>
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#include <boost/assert.hpp>
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#include <boost/core/cmath.hpp>
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#if BOOST_WORKAROUND(BOOST_MSVC, >= 1400)
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# pragma warning(push)
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# pragma warning(disable: 4100) // 'p': unreferenced formal parameter
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# pragma warning(disable: 4127) // conditional expression is constant
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#endif
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namespace boost { namespace spirit { namespace traits
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{
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using spirit::traits::pow10;
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namespace detail
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{
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template <typename T, typename AccT>
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void compensate_roundoff(T& n, AccT acc_n, mpl::true_)
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{
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// at the lowest extremes, we compensate for floating point
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// roundoff errors by doing imprecise computation using T
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int const comp = 10;
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n = T((acc_n / comp) * comp);
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n += T(acc_n % comp);
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}
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template <typename T, typename AccT>
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void compensate_roundoff(T& n, AccT acc_n, mpl::false_)
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{
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// no need to compensate
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n = acc_n;
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}
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template <typename T, typename AccT>
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void compensate_roundoff(T& n, AccT acc_n)
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{
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compensate_roundoff(n, acc_n, is_integral<AccT>());
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}
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}
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template <typename T, typename AccT>
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inline bool
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scale(int exp, T& n, AccT acc_n)
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{
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if (exp >= 0)
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{
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int const max_exp = std::numeric_limits<T>::max_exponent10;
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// return false if exp exceeds the max_exp
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// do this check only for primitive types!
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if (is_floating_point<T>() && (exp > max_exp))
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return false;
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n = acc_n * pow10<T>(exp);
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}
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else
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{
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if (exp < std::numeric_limits<T>::min_exponent10)
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{
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int const min_exp = std::numeric_limits<T>::min_exponent10;
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detail::compensate_roundoff(n, acc_n);
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n /= pow10<T>(-min_exp);
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// return false if exp still exceeds the min_exp
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// do this check only for primitive types!
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exp += -min_exp;
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if (is_floating_point<T>() && exp < min_exp)
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return false;
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n /= pow10<T>(-exp);
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}
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else
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{
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n = T(acc_n) / pow10<T>(-exp);
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}
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}
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return true;
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}
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inline bool
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scale(int /*exp*/, unused_type /*n*/, unused_type /*acc_n*/)
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{
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// no-op for unused_type
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return true;
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}
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template <typename T, typename AccT>
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inline bool
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scale(int exp, int frac, T& n, AccT acc_n)
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{
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return scale(exp - frac, n, acc_n);
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}
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inline bool
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scale(int /*exp*/, int /*frac*/, unused_type /*n*/)
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{
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// no-op for unused_type
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return true;
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}
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inline float
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negate(bool neg, float n)
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{
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return neg ? (core::copysign)(n, -1.f) : n;
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}
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inline double
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negate(bool neg, double n)
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{
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return neg ? (core::copysign)(n, -1.) : n;
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}
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inline long double
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negate(bool neg, long double n)
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{
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return neg ? (core::copysign)(n, static_cast<long double>(-1)) : n;
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}
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template <typename T>
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inline T
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negate(bool neg, T const& n)
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{
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return neg ? -n : n;
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}
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inline unused_type
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negate(bool /*neg*/, unused_type n)
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{
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// no-op for unused_type
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return n;
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}
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template <typename T>
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struct real_accumulator : mpl::identity<T> {};
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template <>
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struct real_accumulator<float>
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: mpl::identity<uint_t<(sizeof(float)*CHAR_BIT)>::least> {};
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template <>
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struct real_accumulator<double>
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: mpl::identity<uint_t<(sizeof(double)*CHAR_BIT)>::least> {};
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}}}
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namespace boost { namespace spirit { namespace qi { namespace detail
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{
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BOOST_MPL_HAS_XXX_TRAIT_DEF(version)
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template <typename T, typename RealPolicies>
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struct real_impl
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{
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template <typename Iterator>
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static std::size_t
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ignore_excess_digits(Iterator& /* first */, Iterator const& /* last */, mpl::false_)
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{
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return 0;
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}
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template <typename Iterator>
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static std::size_t
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ignore_excess_digits(Iterator& first, Iterator const& last, mpl::true_)
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{
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return RealPolicies::ignore_excess_digits(first, last);
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}
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template <typename Iterator>
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static std::size_t
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ignore_excess_digits(Iterator& first, Iterator const& last)
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{
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typedef mpl::bool_<has_version<RealPolicies>::value> has_version;
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return ignore_excess_digits(first, last, has_version());
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}
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template <typename Iterator, typename Attribute>
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static bool
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parse(Iterator& first, Iterator const& last, Attribute& attr,
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RealPolicies const& p)
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{
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if (first == last)
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return false;
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Iterator save = first;
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// Start by parsing the sign. neg will be true if
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// we got a "-" sign, false otherwise.
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bool neg = p.parse_sign(first, last);
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// Now attempt to parse an integer
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T n;
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typename traits::real_accumulator<T>::type acc_n = 0;
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bool got_a_number = p.parse_n(first, last, acc_n);
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int excess_n = 0;
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// If we did not get a number it might be a NaN, Inf or a leading
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// dot.
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if (!got_a_number)
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{
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// Check whether the number to parse is a NaN or Inf
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if (p.parse_nan(first, last, n) ||
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p.parse_inf(first, last, n))
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{
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// If we got a negative sign, negate the number
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traits::assign_to(traits::negate(neg, n), attr);
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return true; // got a NaN or Inf, return early
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}
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// If we did not get a number and our policies do not
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// allow a leading dot, fail and return early (no-match)
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if (!p.allow_leading_dot)
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{
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first = save;
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return false;
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}
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}
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else
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{
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// We got a number and we still see digits. This happens if acc_n (an integer)
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// exceeds the integer's capacity. Collect the excess digits.
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excess_n = static_cast<int>(ignore_excess_digits(first, last));
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}
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bool e_hit = false;
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Iterator e_pos;
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int frac_digits = 0;
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// Try to parse the dot ('.' decimal point)
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if (p.parse_dot(first, last))
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{
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// We got the decimal point. Now we will try to parse
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// the fraction if it is there. If not, it defaults
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// to zero (0) only if we already got a number.
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if (excess_n != 0)
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{
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// We skip the fractions if we already exceeded our digits capacity
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ignore_excess_digits(first, last);
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}
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else if (p.parse_frac_n(first, last, acc_n, frac_digits))
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{
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BOOST_ASSERT(frac_digits >= 0);
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}
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else if (!got_a_number || !p.allow_trailing_dot)
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{
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// We did not get a fraction. If we still haven't got a
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// number and our policies do not allow a trailing dot,
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// return no-match.
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first = save;
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return false;
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}
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// Now, let's see if we can parse the exponent prefix
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e_pos = first;
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e_hit = p.parse_exp(first, last);
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}
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else
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{
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// No dot and no number! Return no-match.
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if (!got_a_number)
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{
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first = save;
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return false;
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}
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// If we must expect a dot and we didn't see an exponent
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// prefix, return no-match.
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e_pos = first;
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e_hit = p.parse_exp(first, last);
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if (p.expect_dot && !e_hit)
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{
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first = save;
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return false;
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}
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}
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if (e_hit)
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{
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// We got the exponent prefix. Now we will try to parse the
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// actual exponent.
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int exp = 0;
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if (p.parse_exp_n(first, last, exp))
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{
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// Got the exponent value. Scale the number by
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// exp + excess_n - frac_digits.
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if (!traits::scale(exp + excess_n, frac_digits, n, acc_n))
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return false;
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}
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else
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{
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// If there is no number, disregard the exponent altogether.
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// by resetting 'first' prior to the exponent prefix (e|E)
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first = e_pos;
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// Scale the number by -frac_digits.
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bool r = traits::scale(-frac_digits, n, acc_n);
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BOOST_VERIFY(r);
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}
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}
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else if (frac_digits)
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{
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// No exponent found. Scale the number by -frac_digits.
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bool r = traits::scale(-frac_digits, n, acc_n);
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BOOST_VERIFY(r);
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}
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else
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{
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if (excess_n)
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{
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if (!traits::scale(excess_n, n, acc_n))
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return false;
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}
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else
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{
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n = static_cast<T>(acc_n);
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}
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}
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// If we got a negative sign, negate the number
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traits::assign_to(traits::negate(neg, n), attr);
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// Success!!!
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return true;
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}
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};
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#if BOOST_WORKAROUND(BOOST_MSVC, >= 1400)
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# pragma warning(pop)
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#endif
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}}}}
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#endif
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