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Re: A value for "nothing"

From: Ludovic Courtès
Subject: Re: A value for "nothing"
Date: Tue, 28 Aug 2018 09:52:21 +0200
User-agent: Gnus/5.13 (Gnus v5.13) Emacs/26.1 (gnu/linux)


Mark H Weaver <address@hidden> skribis:

> address@hidden (Ludovic Courtès) writes:
>> I would suggesting returning zero values, using:
>>   (values)
>> That way, if a caller wrongfully attempts to get at the return value of
>> that procedure, it’ll get an error.
>> Fibers does that in several places, and I think it’s a good convention
>> as it conveys exactly what you want.
> You cannot store (values) in a variable or data structure, so it
> wouldn't work here.
> The issue under discussion is how to represent MessagePack's "nil",
> which is one of the possible values that a MessagePack can have,
> alongside booleans, integers, floats, strings, arrays, etc.

Oops, sorry for the off-topic reply!

In this context, my preference would be for a singleton type:

  (define-record-type <nothing>


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