CREATE CELLS        \ CELLS' stack effect will be ( n -- 2n )
   ' 2* >BODY   runtime

CODE ADEPTH  ( -- N )
   ' AP0 >BODY C@ # LDY,
   SEC,  UP )Y LDA,
   AP0 @ SBC,
   .A LSR,
   APUSH JMP,
END-CODE

: VOCS
   [ ' FORTH >BODY ] LITERAL 0
   .VOCS  CR ;

: (.DEST)  ( ADDR -- )
   AFIND DROP ?DUP
   IF
      ."  ' " L>NAME DUP ID.
      ."  >BODY" NAME> >BODY -
      ?DUP 0EXIT
      SPACE U. ." +"  EXIT
   THEN
   DROP ;

: CREATEDIS  ( CFA -- )
   DUP AFIND NIP
   SWAP - 2- ?DUP
   IF
      OVER @ AFIND DROP
      L>NAME CR ID.
      SPACE 16BITS U.R
      SWAP >BODY  CR ." PFA: "
      16BITS U.R SPACE 16BITS U.R
      EXIT
   THEN
   @ DUP CR (.DEST)  DIS ;

: ?CODE  ( ADDR -- F )
   DUP @ SWAP >BODY = ;

: >DIS  ( CFA -- )
   >BODY DIS ;
   
: >:DIS  ( CFA -- )
   >BODY :DIS ;
   
: DDIS  ( CFA -- )
   ."  DEFERED TO "
   >BODY @ DUP .NAME SPACE U. ;

>BODY
( xt -- a-addr )
a-addr is the data-field address corresponding to xt. An ambiguous condition exists if xt is not for a word defined via CREATE.

                    DEFINITION FIELD ADDRESS CONVERSION OPERATORS

                                         by

                                    Kim R. Harris

          A.  INTRODUCTION

          The standard provides a transportable way to obtain the
          compilation address of a definition in the dictionary of a FORTH
          system (cf., FIND and ' ).  It also provides an operator to
          convert a compilation address to its corresponding parameter
          field address.  However, the standard does not provide a
          transportable way to convert either of these addresses to the
          other fields of a definition.  Since various FORTH
          implementations have different dictionary structures, a standard
          set of conversion operators would increase transportability and
          readability.

          A set of words is proposed which allows the conversion of any
          definitions field address to any other.

          B.  GLOSSARY

          In the following words, the compilation address is either the
          source or the destination, so it is not indicated in the names.

          >BODY        addr1 -- addr2                            "to-body"
               addr2 is the parameter field address corresponding to the
               compilation address addr1.

          >NAME        addr1 -- addr2                            "to-name"
               addr2 is the name field address corresponding to the
               compilation address addr1.

          >LINK        addr1 -- addr2                            "to-link"
               addr2 is the link field address corresponding to the
               compilation address addr1.

          BODY>        addr1 -- addr2                          "from-body"
               addr2 is the compilation address corresponding to the
               parameter field address addr1.

          NAME>        addr1 -- addr2                          "from-name"
               addr2 is the compilation address corresponding to the name
               field address addr1.

          LINK>        addr1 -- addr2                          "from-link"
               addr2 is the compilation address corresponding to the link
               field address addr1.


          The previous set of words is complete, but may be inefficient for
          going between two fields when one is not the compilation address.
          For greater efficiency, additional operators may be defined which
          name both the source and destination fields.

          N>LINK       addr1 -- addr2                       "name-to-link"
               addr2 is the link field address corresponding to the name
               field address addr1.

          L>NAME       addr1 -- addr2                       "link-to-name"
               addr2 is the name field address corresponding to the link
               field address addr1.


          C.  DISCUSSION

          The previous words provide a complete, consistent, and efficient
          set of definition field address conversion operations.  They can
          be implemented in a FORTH system which uses any combination of
          the following options for its dictionary structure:

               Link fields first or second.
               Fixed or variable length name fields.
               Additional fields in the definitions structure.
               Heads contiguous or separated from bodies.
               Indirect, direct, subroutine, or token threaded code.

          The words are compatible with this standard; their inclusion
          would not require other changes to be made to the standard.