At Sat, 09 Apr 2011 21:48:57 +0200, Joel Falcou wrote:
I was thinking lately that it is a shame we can't do the following :
boost::mpl::transform< SomeSequence, _1&>
instead of the lengthy
boost::mpl::transform< SomeSequence, add_reference<_1> >
same goes for *, const, volatile :
boost::mpl::transform< SomeSequence, volatile _1**&>
Could it be possible to get such a behavior in MPL by having a pass of replacing type qualifier by corresponding metafunction until none are left then apply the lambda ?
In the same vein, having a MPL trandform turning a sequence of std::vector into their corresponding value_type require out of line small metafunction to be written. I guess a macro like
BOOST_MPL_ADAPTED_PLACEHOLDER( v, (type)(value_type)(reference)(const_reference) )
builds a whoel familly of _v1, ..., _v5 placeholder which behaves like _n and expose typedef called value_type etc ... that resolve to said small lambda function directly.
This would allow for a terse:
boost::mpl::transform< SomeSequence, _v1::reference>
Are these ideas out of the question due to some internals of MPL I missed ? Are they worthy a patch ?
They sound like great ideas to me. Aleksey? -- Dave Abrahams BoostPro Computing http://www.boostpro.com