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From: Reece Dunn (msclrhd_at_[hidden])
Date: 2004-03-12 07:42:00

Roland Richter wrote:


> I just checked out outfmt from the sandbox CVS and did some
> tests to see whether it works together with lexical_cast.
> The general idea is this:

> Since lexical_cast internally uses a stringstream and its
> associated operators>> and <<, it should be possible to
> cast each type for which these operators are defined;
> and since outfmt defines <</>> for STL container types,
> I tried to combine them in order to convert between strings
> and STL containers.

> After some hassle, it works (under MS VC++ 7.0); see the
> attachment. Issues:

> 1) For reasons I don't completely understand, the compiler
> could not find operator<< from stl_io_basic.hpp when
> compiling lexical_cast.hpp. I had to hack detail/stl_io_basic.hpp
> and put everything in namespace boost::detail (where
> lexical_stream lives).

> BTW, I'm not happy that stl_io.hpp includes everything from
> vector to slist, and that so much code is put into the global
> namespace.

I am aware of this and am working on splitting the code into files like
<boost/outfmt/stl/vector.hpp>, etc. There are three main areas that need to
be split:

[1] The STL I/O code
[2] The type identification code
[3] The get/put helpers for pair-like objects

I have got a version of this to work with MS VC 7.x, but I have a
compilation problem on borland and GCC 2.95.3-5 is generating a "signal 13"
message on the regression tests (I think this is my cygwin setup, but
haven't verified this). I have since been busy and haven't had a chance to
look into these.

I shall move the inserters and extractors to the boost::detail namespace and
will look into the lexical_cast problem.

> 2) The output operator puts spaces after '[', before ']',
> and after each ','; whereas the input operator expects
> no spaces at all; if spaces were present, a bad_lexical_cast
> exception was thrown. I think it is really important that
> operator>> can deal with an output which was generated by <<;
> stated in terms of lexical_cast,
> lexical_cast<T>( lexical_cast<string>( t ) ) == t
> should hold for any T t.

I stripped and skipped the spaces during the read operation to allow for the
read operation to accommodate input variations, e.g. [ a, b ]; [a, b] and [
a,b ] would be read by the same formatter, making it easier to interoperate
with data generated from other sources. I could make this a configurable
option that does not strip the spaces by default.

This should work. If you have examples where it doesn't, please let me know
and I can add it into the regression tests.

NOTE: There is a known defect when handling string data. This may be
generating the problem you are encountering. If you run my regression tests
(libs/outfmt/test/ you should see it as a fail. I am aware of
the problem and am looking into it. (This is made more difficult because the
solution I implemented doesn't work with Borland :()

> I intend to do some further tests, and to give more feedback during
> the IO Formatters formal review (no date is fixed yet, or is it?)

Thanks. I appreciate the feedback. I would like to get the string

>// Copyright Roland Richter 2004.
>// Distributed under the Boost Software License, Version 1.0.
>// (See accompanying file LICENSE_1_0.txt
>// or copy at
>#include <boost/test/minimal.hpp>
>#include <vector>
>#include <string>
>#include <iostream>
>#include <boost/lexical_cast.hpp>
>#include <boost/outfmt/stl_io.hpp>
>// 1) Namespace problem:
>// e:\lib\boost_1_31_0\boost\lexical_cast.hpp(144): error C2679: binary
>'<<' :
>// no operator found which takes a right-hand operand of type 'const
>_STL::vector<_Tp,_Alloc>' (or there is no acceptable conversion)
>// with
>// [
>// _Tp=double,
>// _Alloc=_STL::allocator<double>
>// ]
>// => move everything in boost/outfmt/detail/stl_io_basic.hpp into
>namespace boost::detail
>// 2) operator<< puts spaces after '[' and ',', whereas operator>> expects
>// no spaces at all (otherwise, bad_lexical_cast is thrown).
>void lexical_cast_and_outfmt_test()
> double foos[] = {0.7016, 0.9943, 1.3441, 1.1637, 0.5994, 0.0000,
> std::vector<double> fooVec( foos, foos + 7 );
> std::string fooStr( "[ 0.7016, 0.9943, 1.3441, 1.1637, 0.5994, 0, 0 ]"
> // Output
> std::string castedStr = boost::lexical_cast<std::string>( fooVec );
> BOOST_CHECK( castedStr == fooStr );
> std::string fooStr_WithoutSpaces(
>"[0.7016,0.9943,1.3441,1.1637,0.5994,0,0]" );
> // Input
> std::vector<double> castedVec
> = boost::lexical_cast< std::vector<double> >( fooStr_WithoutSpaces );
> BOOST_CHECK( castedVec == fooVec );
>int test_main( int, char *[] )
> lexical_cast_and_outfmt_test();
> return 0;

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