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Re: Issue: TAGBODY-CONTENTS (Version 3)
- To: Gray@DSG.csc.ti.com
- Subject: Re: Issue: TAGBODY-CONTENTS (Version 3)
- From: Kent M Pitman <KMP@STONY-BROOK.SCRC.Symbolics.COM>
- Date: Wed, 5 Oct 88 15:00 EDT
- Cc: peck@SUN.COM, KMP@STONY-BROOK.SCRC.Symbolics.COM, CL-Cleanup@SAIL.STANFORD.EDU
- In-reply-to: <2801068586-4412902@Kelvin>
Date: Wed, 5 Oct 88 13:36:26 CDT
From: David N Gray <Gray@DSG.csc.ti.com>
> Is anybody concerned about macros that expand to a tagbody with NIL forms?
> If NIL is a statement in a tagbody then they disappear quietly,
> especially after a pass by a good compiler.
> With the current proposal, though, one will get:
> "ERROR: Multiple appearances of tag NIL."
> I don't know what current practice is, if code like this has
> always signalled an error then this is a total non-issue.
> If not, it might be noted as a possible conversion cost.
The Explorer permits using NIL as a GO tag, but as a special case, does
not warn about multiple appearances of NIL.
Hmmm. That suggests another alternative: We could leave NIL being a tag
and just say that it's an error to repeat a tag only if you also GO to
it. That would mean that other tags could be repeated as well. eg, I
seem to recall that some people put ------ in their tagbodies as
separators between major sections. As long as they didn't also do (GO
-----), their practice would be legitimized.