Re: [boost] Plea for addition of stream_cast

From: Bertolt Mildner (Bertolt.Mildner_at_[hidden])
Date: 2000-06-06 13:29:24

----- Original Message ----- 
From: "Mark Rodgers" <mark.rodgers_at_[hidden]>
To: <boost_at_[hidden]>
Sent: Tuesday, June 06, 2000 9:34 AM
Subject: Re: [boost] Plea for addition of stream_cast

> From: Ed Brey <brey_at_[hidden]>
> 
> > What's benefit do you see in avoiding exceptions?  
> 
> I don't think exceptions should be used as a normal control
> mechanism; they should be reserved for exceptional circumstances.

I agree, but hence converting "Fred" in an object of type float is nothing normal I thing we should go for the throwing version of stream_cast.

> > Returning default values on failure is ambiguous, unless you 
> > know from your context that the default would be impossible.  
> 
> Agreed.  But sometimes we may indeed know this:
> 
>       int n = stream_cast<int>(argv[1], 0);
>       if (n < 5)
>       {
>           std::cerr << "x must be a number greater than 4.";
>           return EXIT_FAILURE;
>       }
>
> Do we care whether the user typed "fred" or "3"?  Possibly not.

But what if there is no value that can be used as a return value in case if an error?

An other point I want to mention is that I feel that stream_cast should do what standard casts like dynamic_cast do in case of an unrecoverable error, throwing an object of typ std::bad_cast.

Bertolt