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bug#16158: psyntax: bug in bound-identifier=?
From: |
Mark H Weaver |
Subject: |
bug#16158: psyntax: bug in bound-identifier=? |
Date: |
Mon, 16 Dec 2013 23:03:52 -0500 |
User-agent: |
Gnus/5.13 (Gnus v5.13) Emacs/24.3 (gnu/linux) |
Marco Maggi <address@hidden> writes:
> IMHO it is an error in the paper. Some paragraphs from the paper
> preceding "the one" have been recycled in the R6RS document, but this
> one paragraph has not; maybe this means something.
Interesting. I looked closer, and found this in the R6RS definition of
'bound-identifier=?':
Operationally, two identifiers are considered equivalent by
bound-identifier=? if and only if they have the same name and same
marks (section 12.1).
I also found this in the R6RS errata:
ยง 12.1
The remark "An algebra that defines how marks and substitutions
work more precisely is given in section~2.4 of Oscar Waddell's PhD
thesis." is somewhat misleading and should be qualified as follows:
"Note, however, that Waddell's thesis describes slightly different
semantics for bound-identifier=? - it specifies that for two
identifiers to be equal in the sense of bound-identifier=?, they
must have the same marks and be equal in the sense of
free-identifier=?, whereas this report requires instead that they
must have the same marks and have the same name."
I guess that Kent Dybvig changed his mind about how 'bound-identifier=?'
should behave. I don't fully understand the issues, so I'm inclined to
go along with the R6RS definition.
Therefore, I've reverted 70c74b847680d3b239e591afa2e99c51a712980c.
Thanks,
Mark