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Re: [Chicken-users] New immediate values (was: DBI)

From: Thomas Chust
Subject: Re: [Chicken-users] New immediate values (was: DBI)
Date: Fri, 29 Feb 2008 16:03:11 +0100

On 29. Februar 2008 09:24:07 -0500 John Cowan <address@hidden> wrote:

Alaric Snell-Pym scripsit:

> Gensym values aren't disjoint *in type* from anything else.

Ah, but disjointness in value is all that's required...

Technically yes, but most of us find predicates like number?, string?,
and symbol? rather handy all the same, and don't want NULL mixed up
with them. [...]


this is really a question of taste, isn't it? You could just as well argue that a NULL value should be of a type that is a subtype of every other existing type but contains no other concrete instances, which would imply that all the type predicates should return #t when applied to the NULL value. This makes a lot of sense when the NULL value is used to indicate the absence of an object reference and is the way it is handled in several object oriented languages.


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