Re: [boost] [safebool] Can we generalize it and put it into utilities?

Subject: Re: [boost] [safebool] Can we generalize it and put it into utilities?
From: vicente.botet (vicente.botet_at_[hidden])
Date: 2009-03-29 18:19:43

Hi,
----- Original Message ----- 
From: <Vladimir.Batov_at_[hidden]>
To: <boost_at_[hidden]>
Cc: <Vladimir.Batov_at_[hidden]>
Sent: Sunday, March 29, 2009 11:18 PM
Subject: [boost] [safebool] Can we generalize it and put it into utilities?

> 
> Repeating safe-bool scaffolding over and over again is a real nuisance. It 
> is worse for the end users as not exactly everyone is intimately familiar 
> with the issue and the safe-bool workaround. Can we generalize it and put 
> something like the following into utilities?
> 
> struct safebool
> {
>    typedef void (safebool::*unspecified_bool_type)() const;
>    typedef unspecified_bool_type result;
> 
>    explicit safebool(bool v) : value_(v) {}
> 
>    operator result() const { return value_ ? &safebool::internal_bool : 
> 0; }
> 
>    private:
> 
>    void internal_bool() const {};
> 
>    bool value_;
> };
> 
> That way all we (and the users) will have to do to deploy the technique 
> will be 
> 
> class Foo
> { ...
>    operator safebool::result() const { return safebool(my_condition); }
> };
> 
> This seems simple and hassle-free.

Yes, this seems much more simple and open than the mixin approach. 
Why do you use result instead of unspecified_bool_type. The following it enough clear to me

class Foo
{ ...
  operator safebool::unspecified_bool_type() const { 
    return safebool(my_condition); 
  }
};

I like it anyway,
Vicente