Re: [Chicken-users] handling the undefined value

[Felix]

From: Jörg "F. Wittenberger" <address@hidden>
Subject: Re: [Chicken-users] handling the undefined value
Date: Thu, 25 Nov 2010 16:24:01 +0100

> Am Mittwoch, den 24.11.2010, 18:53 +0100 schrieb Felix:
>> From: Jörg "F. Wittenberger" <address@hidden>
>> Subject: Re: [Chicken-users] handling the undefined value
>> Date: Mon, 22 Nov 2010 15:08:46 +0100
>> 
>> > Have a compiler switch (since it may break some code), which changes the
>> > code to return zero values instead of the distinguished undefined value.
>> 
>> I don't think this is a great idea: this will change the
>> semantics of code using call-with-values,
> 
> So far I did not come around to test, whether or not I'll be able to
> find my undefined value with the new scrutinizer version.

Unfortunately I had to disable this feature again. We probably need
some sort of "style" warning switch (there are too many places where
procedures without result or undefined result use forms like `when').

> 
> Otherwise I'm aware that this would change semantics.  Hence I'd only
> propose it as a switch.
> 
>>  will be less efficient,
> 
> This however I don#t understand.  Why would it be less efficient to call
> a continuation with zero instead of one value?

There is a bit of wrapping and result-value count checking going on
behind the scenes in that case.


cheers,
felix