Re: [Boost-users] [lexical_cast] lexical_cast<int>("1e4") == 1

From: Jeff F (TriumphSprint2000_at_[hidden])
Date: 2007-03-19 08:35:16

Johan Råde wrote:
> Paul Giaccone wrote:
>> n.torrey.pines_at_[hidden] wrote:
>>> lexical_cast<int>("1e4") == 1 // because of the way streams work of
>>> course
>>>
>>> I think that in the interests of robustness, and unless a better
>>> solution can be found, lexical_cast<> should be secialized for some
>>> types.
>>>
>>
>> Interesting... I had exactly the same issue in MEL the other day. The
>> obvious workaround is to cast the string to a float before casting
>> it to an int, but it would be nice if lexical_cast<int> recognised
>> floating-point numbers in scientific notation.
>
>
> C++ iostreams do not support integers in scientific notation.
> There may be good reasons for that:
>
> 1.2345    is not an integer
> 1.2345e4  is an integer
> 1.2345e3  is not an integer
>
> That makes the task of parsing integers in scientific notation a bit
> tricky.

"1e-4" makes the issue even more obvious. Also doesn't "1e4" actually imply 
"1.e4" or "1.0e4"?

I thought there was discussion at one point concerning whether not consuming 
the entire string should be an error condition. Does anyone remember that?

Jeff