Re: [boost] Constructor with parameters -- Lambda

17 Jun 2008

      I believe this is a bug in the boost lambda constructor

I have worked around the problem with this wrapper:

template< typename T >
    struct LambdaConstructorWrapper : public boost::lambda::constructor< T >
    {
        typedef T result_type;
    };

and using it as such:

LambdaConstructorWrapper<MyType> myTypeConstructionWrapper;

                std::transform(
                    mycontainer.begin(),
                    mycontainer.end(),
                    std::back_inserter( redcontainer ),
                    boost::bind(myTypeConstructionWrapper, _1,
WHATEVER_PARM));

It seems to behave as expected by adding this one typedef so it's probably a
bug?  unless by design it's not supposed to be used this way for some reason
that I don't see?

On Mon, Jun 16, 2008 at 9:55 AM, albert meyburgh <ameyburgh@gmail.com>
wrote:
...
Thanks for the input on trying to use boost::lambda::bind instead of
boost::bind, unfortunately there is no bind in the lambda namespace.
I'm using Boost 1.35, and in my version "namespace lambda" only exists in
boost\lambda\construct.hpp and only contains a single templated struct
constructor, there is no bind available :(
Any ideas?
I'm trying all sort of funny syntax variations to no avail...
Message: 4
Date: Fri, 13 Jun 2008 15:37:58 -0700
From: "albert meyburgh" <ameyburgh@gmail.com>
Subject: [boost] Constructor with parameters -- Lambda
To: boost@lists.boost.org
Message-ID:
       <35f053b10806131537o4b85769fg84a88bc0c70dddc4@mail.gmail.com>
Content-Type: text/plain; charset=ISO-8859-1
Hi,
I'm trying to use the lambda constructor provided in boost and it's not
compiling.
class someclass
{
someclass(sometype, int x)
}
std::vector v<sometype>
std::vector v2<someclass>
std::transform( v.begin(),
                   v.end(),
                   std::back_inserter( v2 ),
                   boost::bind( boost::lambda::constructor<someclass>(),
_1, 5) ); // where 5 is a constant int parameter for x to the constructor
Resulting in
Error    1    error C2039: 'result_type' : is not a member of
'boost::lambda::constructor<T>'   boost_1_35_0\boost\bind.hpp    67
Error    2    error C2146: syntax error : missing ';' before identifier
'type'    boost_1_35_0\boost\bind.hpp    67
Error    3    error C4430: missing type specifier - int assumed. Note: C++
does not support default-int    boost_1_35_0\boost\bind.hpp    67
Error    4    error C2208: 'boost::_bi::type' : no members defined using
this type   boost_1_35_0\boost\bind.hpp    67
Error    5    fatal error C1903: unable to recover from previous error(s);
stopping compilation    boost_1_35_0\boost\bind.hpp    67
What is wrong with my syntax?
------------------------------
Message: 5
Date: Fri, 13 Jun 2008 15:57:59 -0700
From: Steven Watanabe <watanabesj@gmail.com>
Subject: Re: [boost] Constructor with parameters -- Lambda
To: boost@lists.boost.org
Message-ID: <4852FB77.4000902@providere-consulting.com>
Content-Type: text/plain; charset=ISO-8859-1; format=flowed
AMDG
albert meyburgh wrote:
...
boost::bind( boost::lambda::constructor<someclass>(),
_1, 5) ); // where 5 is a constant int parameter for x to the constructor
Use boost::lambda::bind.
In Christ,
Steven Watanabe
------------------------------
Message: 6
Date: Fri, 13 Jun 2008 15:59:14 -0700
From: Eric Niebler <eric@boost-consulting.com>
Subject: Re: [boost] Constructor with parameters -- Lambda
To: boost@lists.boost.org
Message-ID: <4852FBC2.8040606@boost-consulting.com>
Content-Type: text/plain; charset=ISO-8859-1; format=flowed
albert meyburgh wrote:
...
Hi,
I'm trying to use the lambda constructor provided in boost and it's not
compiling.
class someclass
{
someclass(sometype, int x)
}
std::vector v<sometype>
std::vector v2<someclass>
std::transform( v.begin(),
                    v.end(),
                    std::back_inserter( v2 ),
                    boost::bind( boost::lambda::constructor<someclass>(),
Try boost::lambda::bind() instead of boost::bind().
--
Eric Niebler
BoostPro Computing
http://www.boostpro.com