sij/mapnik
1
0
Fork 0
Code Issues Pull requests Projects Releases Packages Wiki Activity Actions

Merge pull request #1653 from strk/master-float-scientific

Browse source 
Implement scientific notation for double-to-string
This commit is contained in:
Artem Pavlenko 2012-12-18 02:48:29 -08:00
commit e7891a99ce
2 changed files with 73 additions and 5 deletions
Show stats Download patch file Download diff file Expand all files Collapse all files

74
include/mapnik/util/conversions.hpp
View file

@ -70,12 +70,80 @@ template <typename T>
struct double_policy : boost::spirit::karma::real_policies<T>
{
typedef boost::spirit::karma::real_policies<T> base_type;
static int floatfield(T n) { return base_type::fmtflags::fixed; }
static unsigned precision(T n) { return static_cast<unsigned>(15 - boost::math::trunc(log10(n))); }
static int floatfield(T n) {
using namespace boost::spirit; // for traits
if (traits::test_zero(n))
return base_type::fmtflags::fixed;
T abs_n = traits::get_absolute_value(n);
return (abs_n >= 1e16 || abs_n < 1e-4)
? base_type::fmtflags::scientific : base_type::fmtflags::fixed;
}
static unsigned precision(T n) {
if ( n == 0.0 ) return 0;
using namespace boost::spirit; // for traits
return static_cast<unsigned>(15 - boost::math::trunc(log10(traits::get_absolute_value(n))));
}
template <typename OutputIterator>
static bool dot(OutputIterator& sink, T n, unsigned precision) {
return n ? *sink = '.', true : false;
if (n == 0.0) return true; // avoid trailing zeroes
return base_type::dot(sink, n, precision);
}
template <typename OutputIterator>
static bool fraction_part (OutputIterator& sink, T n
, unsigned precision_, unsigned precision)
{
// NOTE: copied from karma only to avoid trailing zeroes
// (maybe a bug ?)
// allow for ADL to find the correct overload for floor and log10
using namespace std;
using namespace boost::spirit; // for traits
using namespace boost::spirit::karma; // for char_inserter
using namespace boost; // for remove_const
if ( traits::test_zero(n) ) return true; // this part added to karma
// The following is equivalent to:
// generate(sink, right_align(precision, '0')[ulong], n);
// but it's spelled out to avoid inter-modular dependencies.
typename remove_const<T>::type digits =
(traits::test_zero(n) ? 0 : floor(log10(n))) + 1;
bool r = true;
for (/**/; r && digits < precision_; digits = digits + 1)
r = char_inserter<>::call(sink, '0');
if (precision && r)
r = int_inserter<10>::call(sink, n);
return r;
}
template <typename CharEncoding, typename Tag, typename OutputIterator>
static bool exponent (OutputIterator& sink, long n)
{
// NOTE: copied from karma to force sign in exponent
const bool force_sign = true;
using namespace boost::spirit; // for traits
using namespace boost::spirit::karma; // for char_inserter, sign_inserter
long abs_n = traits::get_absolute_value(n);
bool r = char_inserter<CharEncoding, Tag>::call(sink, 'e') &&
sign_inserter::call(sink, traits::test_zero(n)
, traits::test_negative(n), force_sign);
// the C99 Standard requires at least two digits in the exponent
if (r && abs_n < 10)
r = char_inserter<CharEncoding, Tag>::call(sink, '0');
return r && int_inserter<10>::call(sink, abs_n);
}
};

4
tests/cpp_tests/conversions_test.cpp
View file

@ -49,11 +49,11 @@ int main( int, char*[] )
out.clear();
to_string(out, double(1e-05));
BOOST_TEST_EQ( out, "0.00001" );
BOOST_TEST_EQ( out, "1e-05" );
out.clear();
to_string(out, double(-1e-05));
BOOST_TEST_EQ( out, "-0.00001" );
BOOST_TEST_EQ( out, "-1e-05" );
out.clear();
to_string(out, double(0.0001));