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From: "Peter Knaggs" <pjk@bcs.org.uk>
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Subject: RfD: Interpret S\" (Version 2)
Date: Tue, 11 Mar 2014 11:18:39 -0000
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Interpret S\" (Version 2)
=============

20140311 Minor revisions thanks to comments on comp.lang.forth
          from Alex McDonald and Steven Pelc.

20140209 Original Text
          Gerry Jackson, Bernd Paysan and Peter Knaggs


Problem
=======

S" is extended in the File-Access word set to be usable in
interpretation mode.

S\" is a sister word to S" but is not extended in the same way in the
File-Access word set.

It seems to me that S\" is just as useful as S" in interpretation
mode.


Discussion
==========

There are two possible solutions:

Revise the definition of 6.2.2266 S\" to include interpretation
semantics.  Alternatively, add a new entry 11.6.2.2266 S\" which adds
the interpretation action, in the same manner as S".

The interpretation semantics of S" are provided in a separate
definition, so that small systems are not required to implement it.
The same can be said of the interpretation semantics for S\". Thus, we
propose taking the second option, and provide a new definition of S\"
in the FILE word set to provide the interpretation semantics.

This brings us to the question of which buffer should S\" use.  As S\"
is intended as an extension to S" it would make sense to allow S\" to
use the same buffer as S".  The description of the buffer lifetime in
S" will need to be revised.

The number of available buffers is defined as "At least one".  As a
number of FILE words require two strings, this would be the right time
to change this to "at least two".


Solution
========

Provide a new definition in the FILE EXT word set, 11.6.2.2266 S\"
which extends 6.2.2266 S\" by providing interpretation semantics.


Proposal
========

a) Replace 11.3.4 Transient String Buffers:

     The list of words using memory in transient regions is extended to
     include 11.6.1.2165 S". See: 3.3.3.6 Other transient regions.

    with:

     The system provides transient buffers for S" and S\" strings.
     These buffers shall be no less than 80 characters in length,
     and there shall be at least two buffers.  The system should
     be able to store two strings defined by sequential use of S"
     or S\".

b) Add section A.11.3.4 Transient String Buffers

     Additional transient buffers are provided for use by S" and S\".
     The buffers should be able to store two consecutive strings,
     thus allowing the command line:

         S" name1" S" name2" RENAME-FILE

     The buffers may be implemented in a circular arrangement, where
     a string is placed into the next available buffer.  When there
     are no buffers available, the oldest buffer is overwritten.

     S" and S\" may share the same buffers.

     The list of words using memory in transient regions is extended
     to include 11.6.1.2165 S" and 11.6.2.2266 S\".  See 3.3.3.6 Other
     transient regions.

c) Add the following definition to the FILE EXT word set:

     11.6.2.2266 S\"            "s-backslash-quote"            FILE EXT

         Extend the semantics of 6.2.2266 S\" to be:

     Interpretation: ( "ccc<quote>" -- c-addr u )
         Parse ccc delimited by " (double quote) according to the
         translation rules given in 6.2.2266 S\".  Store the resulting
         string in a temporary string buffer (c-addr u).

     Compilation:  ( "ccc<quote>" -- )
         Parse ccc delimited by " (double quote) according to the
         translation rules given in 6.2.2266 S\".  Append the run-time
         semantics given below to the current definition.

     Run-time: ( -- c-addr u )
         Return a string c-addr u describing the translation of ccc.
         A program shall not alter the returned string.

     See: 6.2.2266 S\", 11.3.4 Transient String Buffers, 11.6.1.2165
          S", A.11.3.4 Transient String Buffers.

d) Alter the interpretation semantics of 11.6.1.2165 from:

         Parse ccc delimited by " (double quote). Store the resulting
         string c-addr u at a temporary location. The maximum length
         of the temporary buffer is implementation-dependent but shall
         be no less than 80 characters. Subsequent uses of S" may
         overwrite the temporary buffer. At least one such buffer shall
         be provided.

    to:

         Parse ccc delimited by " (double quote). Store the resulting
         string in a temporary string buffer (c-addr u).

e) Add 11.6.2.2266 S\" and A.11.3.4 Transient String Buffers to the
    see list of 11.6.1.2165 S".

f) Adjust the documentation requirements in 11.4.1.1 Implementation-
    defined options from:

         - number of string buffers provided (11.6.2.2165 S")

         - size of string buffer used by 11.6.1.2165 S".

    to:

         - number of temporary string buffers provided (11.3.4
         Temporary String Buffers)

         - size of temporary string buffers (11.3.4 Temporary String
           Buffers).

g) Replace 3.3.3.4 Text-literal regions with:

         The text-literal regions, specified by strings compiled with
         S", S\" and C", may be read-only.

         A program shall not store into the text-literal regions
         created by S", S\" and C" nor into any read-only system
         variable or read-only transient regions.