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Re: SRFI-108 and SRFI-109 final candidates available

This page is part of the web mail archives of SRFI 108 from before July 7th, 2015. The new archives for SRFI 108 contain all messages, not just those from before July 7th, 2015.

Per Bothner scripsit:

> http://per.bothner.com/tmp/srfi-108/srfi-108.html

s/using same/using the same/
s/specifiction/specification/ (twice)

> http://per.bothner.com/tmp/srfi-109/srfi-109.html


Period did not get added to tag-subsequent.

Rather than referring to R7RS productions, duplicate them in order to help
maintain SRFI 109 as a self-contained document.

Both documents:

Is there a need for [ and ] in SRFI 109 in order to escape
unbalanced brackets in SRFI-108 constructors?

Defining the variables $<<$ and $>>$ as empty strings sounds clever,
but unfortunately none of R[4-7]RS require either `eq?` or `eqv?` to be
able to distinguish between two instances of the empty string.  Scheme
implementations are allowed to coalesce them all into a single instance.
So if they are to be defined as strings, they need to be non-empty if
`$string$` and `$construct:*` are to be definable as functions rather
than as macros.  I suggest:

    ;; Calling string-copy guarantees that these are unique objects.
    (define $<<$ (string-copy "$<<$"))
    (define $>>$ (string-copy "$>>$"))

This means that the sample definition of $string$ has to work a little
harder, skipping arguments that are `eqv?` to either of these variables.
Literal appearances of "$<<$" or "$>>$" in text, or appearances as the
result of evaluating expressions, are guaranteed never to be `eqv?`.

Some people open all the Windows;       John Cowan
wise wives welcome the spring           cowan@xxxxxxxx
by moving the Unix.                     http://www.ccil.org/~cowan
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