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Re: Two minor last-minute tweaks
Mark H Weaver:
> First, a small typo:
> 6. These MUST recurse within lists and vectors, so any list or vector
> in a position that accepts a neoteric expression MUST accept a
> sequence of zero or more neoteric expressions, not just
> s-expressions. (Note that this occurs if they are directly or
> directly within a curly-infix list or a neoteric-expression.) [...]
> Presumably that should be "directly or indirectly", not "directly or
Absolutely correct. Typo fixed.
> An implementation of this SRFI MUST accept the marker #!curly-infix
> followed by a whitespace character in its standard datum readers
> (e.g., read and, if applicable, the default implementation
> REPL). This marker (including the trailing whitespace character)
> MUST be consumed and considered whitespace. After reading this
> marker, the reader MUST accept curly-infix expressions in subsequent
> datums until it reaches an end-of-file or some other conflicting
> marker (no conflicting marker is specified here).
> I'd prefer to change the language "[...] in subsequent datums until it
> reaches an end-of-file [...]" to something closer to "[...] in
> subsequent datums read from the same port [...]". This is based on the
> text in section 2.1 of R7RS (draft 6) that describes #!fold-case and
> These directives may appear anywhere comments are per- mitted (see
> section 2.2) and are treated as comments, except that they affect
> the reading of subsequent data. The #!fold-case directive causes
> the read procedure to case-fold (as if by string-foldcase; see
> section 6.7) each identifier and character name subsequently read
> from the same port. (It has no effect on character literals.) The
> #!no-fold-case directive causes the read procedure to return to the
> default, non-folding behavior.
> There is a functional difference between the two formulations when
> reading from a terminal. On POSIX systems, a terminal device will
> return EOF when CTRL-D is pressed, but then subsequent reads may
> continue to read more data.
> This raises the question of whether the #!curly-infix read option should
> be reset to the Scheme implementation default when CTRL-D is pressed at
> a terminal. I interpret the current language to mean that the flag
> should be reset, but I would prefer that the flag retains its setting as
> long as the port exists.
> Following the R7RS language also simplifies the handling of reader
> directives by giving them uniform behavior, and also makes it crystal
> clear that the flag should be set on a per-port basis (as opposed to a
> global flag for the process or thread).
> What do you think?
Sounds like a great rationale to me. In general, we want to be consistent with how other things are done unless there's a strong reason not to be.
"After reading this marker, the reader <em>MUST</em> accept
curly-infix expressions in subsequent datums
read from the same port until some other conflicting marker is given
(no conflicting marker is specified here)."
--- David A. Wheeler