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Re: [Scheme-reports] Symbol escapes - clarification
- To: Shiro Kawai <shiro.kawai@x>
- Subject: Re: [Scheme-reports] Symbol escapes - clarification
- From: John Cowan <cowan@x>
- Date: Mon, 9 Jan 2012 11:12:07 -0500
- Cc: scheme-reports@x
- In-reply-to: <CALN0JNEO4RAo0YE6=nKri0WApE580Lffn+ZxgdvPuemail@example.com>
- References: <CALN0JNEO4RAo0YE6=nKri0WApE580Lffn+ZxgdvPufirstname.lastname@example.org>
Shiro Kawai scripsit:
> This is a somewhat old issue, but I wonder how '|' symbol escapes
> ended up excluding '|' and '\' inside it. Does it intend a room for
> future extension that vertical bar and backslashes can be included in
> '|' symbol escapes by escaping them with '\', as in CL? I searched
> tickets in the WG1 trac site but couldn't find the discussions on it
> except ticket #16.
I am not sure I understand this. \-escaping *is* allowed within
|-escaping, so |(\x3BB;)| is the identifier "parenthesized lambda".
Indeed, there is a ticket pending to disallow \-escaping by itself and
allow it only within |-escaping. That would allow \ to be an ordinary
> - CL also has '|'-escapes but they don't delimit symbols, so
> |abc|def|ghi| is read as a single symbol abcDEFghi. R7RS doesn't
> explicitly say '|' delimits the symbol, but also doesn't seem to
> allow |abc|def syntax according to 7.1.1. I'm fine with either way,
> but was it a conscious decision?
It was a conscious decision to make vertical bars delimit the symbol, in
the same way that quotes delimit a string. The wording of 2.1 is meant
to imply this: a symbol can begin with |, contain arbitrary characters
or inline hex escapes, and end with |.
Well, I have news for our current leaders John Cowan
and the leaders of tomorrow: the Bill of cowan@x
Rights is not a frivolous luxury, in force http://www.ccil.org/~cowan
only during times of peace and prosperity.
We don't just push it to the side when the going gets tough. --Molly Ivins
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