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Re: Are two symbols `equal' iff they are `eq'?


From: Eli Zaretskii
Subject: Re: Are two symbols `equal' iff they are `eq'?
Date: Sun, 09 Aug 2015 21:19:53 +0300

> From: Marcin Borkowski <address@hidden>
> Date: Sun, 09 Aug 2015 17:45:31 +0200
> 
> >> >From the capitalization I would guess that QUIT is a C macro.  From its
> >> name I would guess that anything after it is irrelevant;-).  Well,
> >> joking aside, I found its definition in the source; do I get it right
> >> that it quits if something like C-g happens?
> >
> > Yes.
> >
> >> If yes, I'd be curious why it is here.
> >
> > To allow the user to interrupt a (potentially) long operation.
> 
> That's obvious, I just wondered why at this point.

Because that point is traversed every recursion, so we check for C-g
on each "iteration", so to say.

> >> Apart from that, it seems that I was right: `equal' for
> >> symbols just calls `eq' (C EQ, not Lisp eq, to be more precise).
> >
> > What else could it possibly do?
> 
> It could e.g. compare the string representation, so two symbols with the
> same name but in different obarrays, or one interned and the other not,
> could be equal but not eq.

I'm sure you understand how all of those would make no sense as
"equality" of any kind.

> (I'm not sure whether this would be useful, though - just a
> thought.)

If it won't be useful, why would someone do it?



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