static bool
parse(Iterator& first, Iterator const& last, Attribute& attr,
RealPolicies const& p)
{
if (first == last)
return false;
Iterator save = first;
// Start by parsing the sign. neg will be true if
// we got a "-" sign, false otherwise.
bool neg = p.parse_sign(first, last);
// Now attempt to parse an integer
T n = 0;
bool got_a_number = p.parse_n(first, last, n);
// If we did not get a number it might be a NaN, Inf or a leading
// dot.
if (!got_a_number)
{
// Check whether the number to parse is a NaN or Inf
if (p.parse_nan(first, last, n) ||
p.parse_inf(first, last, n))
{
// If we got a negative sign, negate the number
traits::move_to(traits::negate(neg, n), attr);
return true; // got a NaN or Inf, return early
}
// If we did not get a number and our policies do not
// allow a leading dot, fail and return early (no-match)
if (!p.allow_leading_dot)
{
first = save;
return false;
}
}
bool e_hit = false;
int frac_digits = 0;
// Try to parse the dot ('.' decimal point)
if (p.parse_dot(first, last))
{
// We got the decimal point. Now we will try to parse
// the fraction if it is there. If not, it defaults
// to zero (0) only if we already got a number.
Iterator savef = first;
if (p.parse_frac_n(first, last, n))
{
// 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));
}
else if (!got_a_number || !p.allow_trailing_dot)
{
// We did not get a fraction. If we still haven't got a
// number and our policies do not allow a trailing dot,
// return no-match.
first = save;
return false;
}
// Now, let's see if we can parse the exponent prefix
e_hit = p.parse_exp(first, last);
}
else
{
// No dot and no number! Return no-match.
if (!got_a_number)
{
first = save;
return false;
}
// If we must expect a dot and we didn't see an exponent
// prefix, return no-match.
e_hit = p.parse_exp(first, last);
if (p.expect_dot && !e_hit)
{
first = save;
return false;
}
}
if (e_hit)
{
// We got the exponent prefix. Now we will try to parse the
// actual exponent. It is an error if it is not there.
int exp = 0;
if (p.parse_exp_n(first, last, exp))
{
// Got the exponent value. Scale the number by
// exp-frac_digits.
traits::scale(exp, frac_digits, n);
}
else
{
// Oops, no exponent, return no-match.
first = save;
return false;
}
}
else if (frac_digits)
{
// No exponent found. Scale the number by -frac_digits.
traits::scale(-frac_digits, n);
}
else if (traits::is_equal_to_one(n))
{
// There is a chance of having to parse one of the 1.0#...
// styles some implementations use for representing NaN or Inf.
// Check whether the number to parse is a NaN or Inf
if (p.parse_nan(first, last, n) ||
p.parse_inf(first, last, n))
{
// If we got a negative sign, negate the number
traits::move_to(traits::negate(neg, n), attr);
return true; // got a NaN or Inf, return immediately
}
}
// If we got a negative sign, negate the number
traits::move_to(traits::negate(neg, n), attr);
// Success!!!
return true;
}
static bool
parse(Iterator& first, Iterator const& last, Attribute& attr,
RealPolicies const& p)
{
if (first == last)
return false;
Iterator save = first;
// Start by parsing the sign. neg will be true if
// we got a "-" sign, false otherwise.
bool neg = p.parse_sign(first, last);
// Now attempt to parse an integer
T n;
typename traits::real_accumulator<T>::type acc_n = 0;
bool got_a_number = p.parse_n(first, last, acc_n);
// If we did not get a number it might be a NaN, Inf or a leading
// dot.
if (!got_a_number)
{
// Check whether the number to parse is a NaN or Inf
if (p.parse_nan(first, last, n) ||
p.parse_inf(first, last, n))
{
// If we got a negative sign, negate the number
traits::assign_to(traits::negate(neg, n), attr);
return true; // got a NaN or Inf, return early
}
// If we did not get a number and our policies do not
// allow a leading dot, fail and return early (no-match)
if (!p.allow_leading_dot)
{
first = save;
return false;
}
}
bool e_hit = false;
Iterator e_pos;
int frac_digits = 0;
// Try to parse the dot ('.' decimal point)
if (p.parse_dot(first, last))
{
// We got the decimal point. Now we will try to parse
// the fraction if it is there. If not, it defaults
// to zero (0) only if we already got a number.
if (p.parse_frac_n(first, last, acc_n, frac_digits))
{
}
else if (!got_a_number || !p.allow_trailing_dot)
{
// We did not get a fraction. If we still haven't got a
// number and our policies do not allow a trailing dot,
// return no-match.
first = save;
return false;
}
// Now, let's see if we can parse the exponent prefix
e_pos = first;
e_hit = p.parse_exp(first, last);
}
else
{
// No dot and no number! Return no-match.
if (!got_a_number)
{
first = save;
return false;
}
// If we must expect a dot and we didn't see an exponent
// prefix, return no-match.
e_pos = first;
e_hit = p.parse_exp(first, last);
if (p.expect_dot && !e_hit)
{
first = save;
return false;
}
}
if (e_hit)
{
// We got the exponent prefix. Now we will try to parse the
// actual exponent.
int exp = 0;
if (p.parse_exp_n(first, last, exp))
{
// Got the exponent value. Scale the number by
// exp-frac_digits.
if (!traits::scale(exp, frac_digits, n, acc_n))
return false;
}
else
{
// If there is no number, disregard the exponent altogether.
// by resetting 'first' prior to the exponent prefix (e|E)
first = e_pos;
n = static_cast<T>(acc_n);
}
}
else if (frac_digits)
{
// No exponent found. Scale the number by -frac_digits.
traits::scale(-frac_digits, n, acc_n);
}
else if (traits::is_equal_to_one(acc_n))
{
// There is a chance of having to parse one of the 1.0#...
// styles some implementations use for representing NaN or Inf.
// Check whether the number to parse is a NaN or Inf
if (p.parse_nan(first, last, n) ||
p.parse_inf(first, last, n))
{
// If we got a negative sign, negate the number
traits::assign_to(traits::negate(neg, n), attr);
return true; // got a NaN or Inf, return immediately
}
n = static_cast<T>(acc_n);
}
else
{
n = static_cast<T>(acc_n);
}
// If we got a negative sign, negate the number
traits::assign_to(traits::negate(neg, n), attr);
// Success!!!
return true;
}