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

Implement scientific notation for double-to-string

Browse source 
Also fixes tests for 1e5 expecting fixed precision rather than
scientific notation (stringstream gives scientific notation indeed)

The only still failing test now is the one having less than 16
significant digits of precision, due to the boost bug:
https://svn.boost.org/trac/boost/ticket/7785
This commit is contained in:
Sandro Santilli 2012-12-17 19:29:44 +01:00
parent 4040eebf10
commit e8b7b82bbb
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));