2010-03-17  Revised after clf discussions.
2010-02-24  Drafting of RfD
2009-09-03  Original wordsmithing of solution during 200x meeting.

Problem
=======

The X:structures extension defines FIELD: as:

   10.6.2.xxxx FIELD:          "field-colon"              FACILITY EXT
               ( -- )                                     X:structures

     The semantics of FIELD: are identical to the execution semantics
     of the phrase:

         ALIGNED 1 CELLS +FIELD

   See: 10.6.2.---- +FIELD, 10.6.2.---- BEGIN-STRUCTURE and
        10.6.2.---- END-STRUCTURE.

While this is a very concise definition, there are a few difficulties
with it:

1) The stack description is incorrect, it should be:
    ( n1 "<spaces>name" -- n2 )

2) It defines a child word which is not described.  Normally this is
    described in a "name Execution" clause.

3) There is no actual description of the word, simply what amounts
    to a reference implementation.

This applies to CFIELD:, DFFIELD:, FFIELD: and SFFIELD: as well.

Solution
========

Replace the definition of FIELD: and friends with:

   10.6.2.xxxx FIELD:          "field-colon"              FACILITY EXT
               ( n1 "<spaces>name" -- n2 )                X:structures

     Skip leading space delimiters.  Parse /name/ delimited by a space.
     Create a definition for /name/ with the execution semantics
     defined below.  n1 is the /offset/ from the start of a data
     structure to place the new field.  If n1 is not a cell aligned
     offset it should be modified to be so.  n2 is the next available
     offset after reserving sufficient space for a single cell in the
     data structure.

     FIELD: creates a single cell field in a data structure.  The
     execution semantics are identical to:

         ALIGNED 1 CELLS +FIELD

   name Execution: ( a-addr1 -- a-addr2 )
     Add the /offset/ calculated during the compile time action to
     a-addr1 giving the cell aligned address a-addr2.

   See: 10.6.2.---- +FIELD, 10.6.2.---- BEGIN-STRUCTURE,
        10.6.2.---- END-STRUCTURE, A.10.6.---- BEGIN-STRUCTURE.

Proposal
========

Modify the definition of the following words in accordance with the
text given in the Solution, above, with the modification of the
alignment as follows:

FIELD:      cell aligned
CFIELD:     character aligned
FFIELD:     float aligned
SFFIELD:    single-float aligned
DFFIELD:    double-float aligned