Float & # 8596; std :: string conversion alternative?

Question

is there an alternative to atof , strtod , lexical_cast , stringstream or sprintf ?

i.e:

• fast
• C ++ way ( std::string instead of char* )
• safe (no risk of buffer overflows)
• valid (returns NaN if the conversion cannot be completed)
• no external library (independent)

I prefer this more, a simple function, optimized and dot

cause:

• atof and strtod is a C function and they do not return NaN after a crash, I prefer to work with std::string , so I just ask if someone already writes some wrapper to std::string that I can use (if you don't mind).
• lexical_cast has a higher dependency
• stringstream slow
• sprintf has a buffer overflow risk and its C function

Answer 1

I would look at Boost Spirit

• http://www.boost.org/doc/libs/1_47_0/libs/spirit/doc/html/spirit/qi/reference/numeric/real.html

At least the control values ​​of the formatter (i.e. float → string) are sequentially displayed as the top of the count * ¹ *

Also, the exact definition of the input format and semantics during parsing can be very well configured using the policy class.

---

Here is my absolute use of min-dependity qi :: any_real_parser <> and a list of dependencies that it touches:

 #include <boost/spirit/include/qi_real.hpp> namespace qi = boost::spirit::qi; int main() { const char input[] = "3.1415926"; const char *f(input); const char *l(f+strlen(input)); qi::any_real_parser<double> x; double parsed; x.parse(f, l, qi::unused, qi::unused, parsed); return 0; } 

<sub>

• promotion / concept
• boost / configuration
• boost / detail
• pushing / dropping
• increase / merge
• push / iterator
• boost / math
• boost / mpl
• nudge / optional
• boost / preprocessor
• boost / proto
• gain / range
• boost / regex
• impulse / spirit
• boost / typeof
• boost / type _traits
• enhancement / utility
• boost / option

aligned_storage.hpp, assert.hpp, blank_fwd.hpp, blank.hpp, call_traits.hpp, checked_delete.hpp, concept_check.hpp, config.hpp, cstdint.hpp, current_function.hpp, foreach_fwd.hpp, foreach.hpp, get_pointer. hpp, implicit_cast.hpp, iterator.hpp, limits.hpp, math_fwd.hpp, next_prior.hpp, noncopyable.hpp, none.hpp, none_t.hpp, optional.hpp, ref.hpp, static_assert.hpp, swap .hpp, throw_exception.hpp, type.hpp, utility.hpp, variant.hpp, version.hpp

sub>

¹ , for example. http://www.boost.org/doc/libs/1_47_0/libs/spirit/doc/html/spirit/karma/performance_measurements/numeric_performance/double_performance.html

Answer 2

If you want to convert from numeric types to std :: string, then there is a function std::to_string , available in the latest standard.

Unfortunately, as I found out recently, in Visual Studio 2010 it is somewhat limited, because only three overloads are available to it; long double, long long and unsigned long. This causes problems when trying to use them from templates.

Answer 3

The fast format library should be able to perform the kind of conversions you are looking for, at least for writing a float. However, it does not handle float parsing.