Re: [boost] [TypeErasure] Forward constructors and binded types

Subject: Re: [boost] [TypeErasure] Forward constructors and binded types
From: Steven Watanabe (watanabesj_at_[hidden])
Date: 2012-07-19 10:55:14

AMDG

On 07/19/2012 07:36 AM, Larry Evans wrote:
> 
> 
> http://steven_watanabe.users.sourceforge.net/type_erasure/libs/type_erasure/example/construction.cpp
> 
> was most helpful to me.  The attached shows
> that 2 different bindings can be used to create
> 2 arguments to a construction of the 3ird placeholder,
> and it still works.  I would have thought that
> the same bindings would have been required for the
> placeholders.

They are.  This happens to work because
I cheated a little in the assertions,
but it's really undefined behavior.

>  The attached produces output of:
> 
> St5dequeIdSaIdEE
> 
> suggesting the type constructed comes from the 1st
> placeholder.  When the code is changed to:
> 
>     any<construct, _b> size(10, bindings1);
>     any<construct, _c> val(2.5, bindings2);
> 
> the output is:
> 
> St6vectorIdSaIdEE
> 
> supporting the above conclusion.
> 
> Do the docs say anywhere that this is what
> happens when 2 different bindings are used
> to construct something?
> 

http://steven_watanabe.users.sourceforge.net/type_erasure/libs/type_erasure/doc/html/boost/type_erasure/any.html#id2370327-bb

"The bindings of all the arguments that are any's, must be the same."

In Christ,
Steven Watanabe