Re: [boost] Result of boost::split against empty string changed in post-1.45 release

Subject: Re: [boost] Result of boost::split against empty string changed in post-1.45 release
From: Marshall Clow (mclow.lists_at_[hidden])
Date: 2012-06-11 23:48:54

On Jun 11, 2012, at 1:26 PM, Mateusz Loskot wrote:
> On 11 June 2012 19:09, Pavol Droba <droba_at_[hidden]> wrote:
>> On Mon, 11 Jun 2012 16:58:40 +0200, Mateusz Loskot <mateusz_at_[hidden]> wrote:
>>> 
>>> I have a simple program runs boost::split against empty string.
>>> I'm testing with Boost 1.45 and later versions like 1.46 or 1.49.
>>> As stated in the // comment below, there is difference in behaviour
>>> depending on the Boost version:
>>> 
>>> // https://gist.github.com/2910461
>>> #include <cassert>
>>> #include <string>
>>> #include <vector>
>>> #include <boost/algorithm/string/split.hpp>
>>> #include <boost/algorithm/string/classification.hpp>
>>> 
>>> int main(int argc, wchar_t* argv[])
>>> {
>>>    std::wstring s;
>>>    std::vector<std::wstring> a;
>>> 
>>>    assert(s.empty());
>>>    boost::split(a, s, boost::is_any_of(L", "), boost::token_compress_on);
>>>    // Boost 1.45:  true
>>>    // Boost 1.46+: false
>>>    //   Assertion failed: s.empty() == a.empty(), file
>>> boost_split_empty_string.cpp, line 16
>>>    assert(s.empty() == a.empty());
>>>    return 0;
>>> }
>>> 
>>> IMHO, the behaviour exposed in newer versions is a bug.
>>> Could anyone shed light on what happened in post-1.46?
>> 
>> 
>> Please search the boos archives. There was an extensive discussion about
>> this particular issue.
> 
> Pavol,
> 
> You are right, there are some discussions about this behavior,
> For example
> 
> http://lists.boost.org/Archives/boost/2005/01/79380.php
> https://svn.boost.org/trac/boost/ticket/534
> 
> and others. Thanks for pointing that.
> 
> I have to admit that to me the current behavior is not intuitive.
> Also, I have failed to find any example of it in the docs.

Mateusz --

If you would be willing to write up a paragraph making this clear, I will put it into the docs.

-- Marshall

Marshall Clow     Idio Software   <mailto:mclow.lists_at_[hidden]>

A.D. 1517: Martin Luther nails his 95 Theses to the church door and is promptly moderated down to (-1, Flamebait).
        -- Yu Suzuki