[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]
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) |
Hello,
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>
(nothing)
nothing?)
Ludo’.
- Re: A value for "nothing", (continued)
Re: A value for "nothing", HiPhish, 2018/08/26