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Re: Behavior of #!optional


From: Théo Cavignac
Subject: Re: Behavior of #!optional
Date: Mon, 9 Mar 2020 22:23:48 +0100
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.5.0

Thank you Evan. By the way I just realized that `#!optional` is specific to chicken anyway which makes this behavior a lot more viable if chicken users already use it.

Cheers,

Théo

Le 03/03/2020 à 09:21, Evan Hanson a écrit :
Hi Théo,

I don't know whether there are any firm guarantees about that behaviour,
but functionally it's safe to rely on, yes. That idiom you mentioned is
pretty handy, I use it myself sometimes.

Under the hood, #!optional arguments are expanded in a let*-style
binding form (as opposed to a "normal" let binding, where they wouldn't
see one another), so later values can refer to earlier ones.

Cheers,

Evan



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