boost/spirit/home/qi/numeric/real_policies.hpp
/*=============================================================================
Copyright (c) 2001-2019 Joel de Guzman
Copyright (c) 2001-2011 Hartmut Kaiser
Distributed under the Boost Software License, Version 1.0. (See accompanying
file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
==============================================================================*/
#ifndef BOOST_SPIRIT_QI_NUMERIC_REAL_POLICIES_HPP
#define BOOST_SPIRIT_QI_NUMERIC_REAL_POLICIES_HPP
#if defined(_MSC_VER)
#pragma once
#endif
#include <boost/spirit/home/qi/numeric/numeric_utils.hpp>
#include <boost/spirit/home/qi/detail/string_parse.hpp>
#include <boost/type_traits/is_floating_point.hpp>
namespace boost { namespace spirit { namespace traits
{
// So that we won't exceed the capacity of the underlying type T,
// we limit the number of digits parsed to its max_digits10.
// By default, the value is -1 which tells spirit to parse an
// unbounded number of digits.
template <typename T, typename Enable = void>
struct max_digits10
{
static int const value = -1; // unbounded
};
template <typename T>
struct max_digits10<T
, typename enable_if_c<(is_floating_point<T>::value)>::type>
{
static int const digits = std::numeric_limits<T>::digits;
static int const value = 2 + (digits * 30103l) / 100000l;
};
}}}
namespace boost { namespace spirit { namespace qi
{
///////////////////////////////////////////////////////////////////////////
// Default (unsigned) real number policies
///////////////////////////////////////////////////////////////////////////
template <typename T>
struct ureal_policies
{
// Versioning
typedef mpl::int_<2> version;
// trailing dot policy suggested by Gustavo Guerra
static bool const allow_leading_dot = true;
static bool const allow_trailing_dot = true;
static bool const expect_dot = false;
template <typename Iterator>
static bool
parse_sign(Iterator& /*first*/, Iterator const& /*last*/)
{
return false;
}
template <typename Iterator, typename Attribute>
static bool
parse_n(Iterator& first, Iterator const& last, Attribute& attr_)
{
typedef extract_uint<Attribute, 10, 1
, traits::max_digits10<T>::value // See notes on max_digits10 above
, false, true>
extract_uint;
return extract_uint::call(first, last, attr_);
}
// ignore_excess_digits (required for version > 1 API)
template <typename Iterator>
static std::size_t
ignore_excess_digits(Iterator& first, Iterator const& last)
{
Iterator save = first;
if (extract_uint<unused_type, 10, 1, -1>::call(first, last, unused))
return static_cast<std::size_t>(std::distance(save, first));
return 0;
}
template <typename Iterator>
static bool
parse_dot(Iterator& first, Iterator const& last)
{
if (first == last || *first != '.')
return false;
++first;
return true;
}
template <typename Iterator, typename Attribute>
static bool
parse_frac_n(Iterator& first, Iterator const& last, Attribute& attr_, int& frac_digits)
{
Iterator savef = first;
bool r = extract_uint<Attribute, 10, 1, -1, true, true>::call(first, last, attr_);
if (r)
{
#if defined(_MSC_VER) && _MSC_VER < 1900
# pragma warning(push)
# pragma warning(disable: 4127) // conditional expression is constant
#endif
// Optimization note: don't compute frac_digits if T is
// an unused_type. This should be optimized away by the compiler.
if (!is_same<T, unused_type>::value)
frac_digits =
static_cast<int>(std::distance(savef, first));
#if defined(_MSC_VER) && _MSC_VER < 1900
# pragma warning(pop)
#endif
// ignore extra (non-significant digits)
extract_uint<unused_type, 10, 1, -1>::call(first, last, unused);
}
return r;
}
template <typename Iterator>
static bool
parse_exp(Iterator& first, Iterator const& last)
{
if (first == last || (*first != 'e' && *first != 'E'))
return false;
++first;
return true;
}
template <typename Iterator>
static bool
parse_exp_n(Iterator& first, Iterator const& last, int& attr_)
{
return extract_int<int, 10, 1, -1>::call(first, last, attr_);
}
///////////////////////////////////////////////////////////////////////
// The parse_nan() and parse_inf() functions get called whenever
// a number to parse does not start with a digit (after having
// successfully parsed an optional sign).
//
// The functions should return true if a Nan or Inf has been found. In
// this case the attr should be set to the matched value (NaN or
// Inf). The optional sign will be automatically applied afterwards.
//
// The default implementation below recognizes representations of NaN
// and Inf as mandated by the C99 Standard and as proposed for
// inclusion into the C++0x Standard: nan, nan(...), inf and infinity
// (the matching is performed case-insensitively).
///////////////////////////////////////////////////////////////////////
template <typename Iterator, typename Attribute>
static bool
parse_nan(Iterator& first, Iterator const& last, Attribute& attr_)
{
if (first == last)
return false; // end of input reached
if (*first != 'n' && *first != 'N')
return false; // not "nan"
// nan[(...)] ?
if (detail::string_parse("nan", "NAN", first, last, unused))
{
if (first != last && *first == '(')
{
// skip trailing (...) part
Iterator i = first;
while (++i != last && *i != ')')
;
if (i == last)
return false; // no trailing ')' found, give up
first = ++i;
}
attr_ = std::numeric_limits<T>::quiet_NaN();
return true;
}
return false;
}
template <typename Iterator, typename Attribute>
static bool
parse_inf(Iterator& first, Iterator const& last, Attribute& attr_)
{
if (first == last)
return false; // end of input reached
if (*first != 'i' && *first != 'I')
return false; // not "inf"
// inf or infinity ?
if (detail::string_parse("inf", "INF", first, last, unused))
{
// skip allowed 'inity' part of infinity
detail::string_parse("inity", "INITY", first, last, unused);
attr_ = std::numeric_limits<T>::infinity();
return true;
}
return false;
}
};
///////////////////////////////////////////////////////////////////////////
// Default (signed) real number policies
///////////////////////////////////////////////////////////////////////////
template <typename T>
struct real_policies : ureal_policies<T>
{
template <typename Iterator>
static bool
parse_sign(Iterator& first, Iterator const& last)
{
return extract_sign(first, last);
}
};
template <typename T>
struct strict_ureal_policies : ureal_policies<T>
{
static bool const expect_dot = true;
};
template <typename T>
struct strict_real_policies : real_policies<T>
{
static bool const expect_dot = true;
};
}}}
#endif
