>You could do it using expression templates. It should be quite easy to
>do and very efficient if you aren't going to need to do type-erasure.
Thanks for the response. I thought about it but I'm not so sure this would solve it.
I have to generate the expression in steps and the corresponding types are based on runtime parameters so they are not known at compile time.
Anyway boost::lambda is based on expression templates so I would like to use that instead of duplicating it.

cheers

Arnaldur


"Felipe Magno de Almeida" <felipe.m.almeida@gmail.com>
Sent by: boost-users-bounces@lists.boost.org

18.10.2006 19:45
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Re: [Boost-users] creating lambda expressions incrementally





On 10/17/06, Arnaldur Gylfason <arnaldur.gylfason@decode.is> wrote:
>
> Hi,
>
> I´m writing a simple expression parser in boost::spirit that can parse a
> string like "_1 + _2" or "log(_1)" and return a function object that does
> just that.
> I used boost::lamda for that and return it as boost::function object.
> Now I want to parse compositions like "sqrt(_1*_1 + _2*_2)" or "(_1 +
> _2)*_2" etc. It is easy to parse this of course but I have to create the
> corresponding function incrementally (in a loop or recursively)
> and that means I have to keep incremental lambdas until the whole expression
> has been created.
> I can not store them as boost::function since they do not work with lambda
> operator overloading (apart from the fact that it would be too costly).
> I need a lambda type for these intermediate lambda objects. I guess the auto
> type specifier would solve this but when will that be available I wonder?
> The typeof seems to provide a solution though. I was just trying it and it
> seems to work!
> Am I on the right track or am I overlooking something? If anyone knows a
> better solution please tell me!

You could do it using expression templates. It should be quite easy to
do and very efficient if you aren't going to need to do type-erasure.

>
> cheers
>
> Arnaldur Gylfason

--
Felipe Magno de Almeida
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