This rips out the Bost Spirit / Karma conversion code, using the stdlib
and lightweight alternatives instead.
The main benefit is an immense decrease in compilation times, for every
translation unit that requires the `util/cast.hpp` header.
Note: compared to the version before, there is a minor change in
behavior: the double `-0` was printed as `0` before and is now printed
as `-0`. This comes from the IEE754 standard, specifying signed zeros,
that is `+0` and `-0`. Interesting for us: JavaScript uses IEE754,
resulting in no breakage if used in arithmetic.
Small test case, left hand side was before, right hand side is now:
$ ./a.out
-1.123457 vs -1.123457
-1 vs -1
-1.3 vs -1.3
0 vs -0
0 vs 0
0 vs 0
1.3 vs 1.3
1.123457 vs 1.123457
References:
- https://en.wikipedia.org/wiki/Signed_zero
- http://www.boost.org/doc/libs/1_59_0/doc/html/boost/algorithm/trim_right_if.html
- http://www.boost.org/doc/libs/1_59_0/doc/html/boost/algorithm/is_any_of.html
With C++11 the stdlib gains:
- `std::stoi` function family to convert from `std::string` to integral type
- `std::to_string` to convert from number types to `std::string`
The only reason for hand-writing the conversion code therefore is
performance. I benchmarked an `osrm-extract` with the hand-written code
against one with the stdlib conversion features and could not find any
significant difference (we switch back and forth between C++ and Lua,
shaving off a few us in conversion doesn't gain us much).
Formatting arithmetic types in the default format with given precision
requires streams, but is doable in a few lines of idiomatic stdlib code.
For this, there is now the following function template available:
template <Arithmetic T, int Precision = 6>
inline std::string to_string_with_precision(const T);
that requires integral or floating point types and returns a formatted
string in the defaukt format with the given precision applied.
In addition this completely rips out Boost.Spirit from the `casts.hpp`
header, resulting in faster compile times.
Boom!
References:
- http://en.cppreference.com/w/cpp/string/basic_string/stol
- http://en.cppreference.com/w/cpp/string/basic_string/to_string
- http://www.kumobius.com/2013/08/c-string-to-int/
