Re: [Boost-users] [optional] mixed (optional<T>, T)-operator== missing by design?

From: Pablo Aguilar (pablo.aguilar_at_[hidden])
Date: 2006-03-14 05:13:53

Wouldn't the following work?

        if( t && *t == mT )

Pablo Aguilar

Marc Mutz wrote:
> Hi,
> 
> In 1.33.1, comparing an optional<T> to it's T fails, since although T 
> implicitly converts to optional<T>, op== being templated, implicit 
> conversions are not considered. Is this by design? If so, what's the 
> rationale for this? I repeatedly find myself in the need to compare an 
> optional<T> member to a passed in T, e.g. in a setT( const T & ), in order to 
> check for a no-op operation and suppress notifications in this case, e.g.:
> 
> class Foo {
>   boost::optional<T> mT;
>   boost::signal< void(const optional<T>&) > tChangedSignal;
>   void setT( const T & t ) {
>     if ( t == mT ) return;
>     mT = t;
>     tChangedSignal( mT );
>     // mark cached values dirty, etc, etc...
>   }
> };
>