Re: [Chicken-hackers] deprecation of always?, never?, none?

[Felix]

From: Thomas Chust <address@hidden>
Subject: Re: [Chicken-hackers] deprecation of always?, never?, none?
Date: Mon, 22 Aug 2011 20:09:30 +0200

> Felix wrote:
>> From: Thomas Chust <address@hidden>
>>> [...]
>>> for example, in the context of type checking, you may want to
>>> represent the fact that a function can never exit through its return
>>> continuation by assigning the none return type to it.
>> 
>> That's a matter of control flow, not of type. Bottom is not a value,
>> it is undefinedness, in every sense.
>> [...]
> 
> Hello,
> 
> well, I think it's both a matter of control flow and types. The border
> between those things is fuzzy, anyway. I suspect that any statement
> about the control flow of a program can be expressed as a type if the
> type system is sufficiently complex.

Yes, that's right. But giving a type to an expression that does not
return is sort of strange: it is values that have a type, and such
an expression has no value. 

So, to get back to the original question: we have an "absence of a
value" which, IMHO, doesn't deserve a value predicate.


cheers,
felix