Re: Bug in real_parser

On 17-09-16 15:28, peterkochlarsen wrote:
> Now as_double("045.000W") returns 45, but as_double("045.000E") returns
> 45000.

I don't believe that for a second. Firstly the code doesn't compile (`d`
is undeclared). Secondly, on correct input it will return `-1`. I think
you need better backup to claim bugs.

Here's what I think you're trying to do, and the results are FINE if you
check the errors:

#include <boost/spirit/include/qi.hpp>
#include <iostream>

double as_double(std::string const& s)
{
    namespace qi = boost::spirit::qi;

    double d;
    auto begin = std::begin(s);
    if (qi::phrase_parse(begin, std::end(s), qi::double_/* >> qi::eoi*/,
qi::space, d))
        return d;
    return -1;
}

int main()
{
    for (std::string const& s : {
            "4",  "04",  "045.",  ".0",  "7E0",  "7.E0",
            "-4", "-04", "-045.", "-.0", "-7E0", "-7.E0",
            "+4", "+04", "+045.", "+.0", "+7E0", "+7.E0",
            "-4", "-04", "-045.", "-.0", "-7E0", "-7.E0",
            ".4e7", ".4e-7",
            // and then your case
            "045.000W",
            "045.000E",
        })
    {
        auto d = as_double(s);
        std::cout << "'" << s << "' -> " << d;
        if (d == -1)
            std::cout << " (ERR)\n";
        else
            std::cout << "\n";
    }
}

Prints

    '4' -> 4
    '04' -> 4
    '045.' -> 45
    '.0' -> 0
    '7E0' -> 7
    '7.E0' -> 7
    '-4' -> -4
    '-04' -> -4
    '-045.' -> -45
    '-.0' -> -0
    '-7E0' -> -7
    '-7.E0' -> -7
    '+4' -> 4
    '+04' -> 4
    '+045.' -> 45
    '+.0' -> 0
    '+7E0' -> 7
    '+7.E0' -> 7
    '-4' -> -4
    '-04' -> -4
    '-045.' -> -45
    '-.0' -> -0
    '-7E0' -> -7
    '-7.E0' -> -7
    '.4e7' -> 4e+06
    '.4e-7' -> 4e-08
    '045.000W' -> 45
    '045.000E' -> -1 (ERR)

If you insist that `045.000W` should fail (why?) then you should
probably write your parser to indicate it (you can also check that the
`begin` iterator is equal to `s.end()`):

    if (qi::phrase_parse(begin, std::end(s), qi::double_ >> qi::eoi,
qi::space, d))


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