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    Types: TextFile
    Names: »PARSER.I«

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TextFile

"-----------------------------------------------------------------------
"
"
"  MODULE NAME:      BOTTOM UP PARSER
"  MODULE ID NMB:    CSS/210
"  MODULE VERSION:   1
"  MODULE TYPE:      IMPORT MODULE
"  MERGE  FILES:     -
"  
"  SPECIFICATIONS:   -
"  AUTHOR/DATE:      LKN/800627
"
"  DELIVERABLE:      YES
"  SOURCE LANGUAGE:  SWELL
"  COMPILE COMPUTER: CR80
"  TARGET COMPUTER:  CR80
"  OPER. SYSTEM:     -
"
"-----------------------------------------------------------------------
"
"  CHANGE RECORD
"
"  VERSION    AUTHOR/DATE    DESCRIPTION OF CHANGE
"  -------    -----------    ---------------------
"
"-----------------------------------------------------------------------
"PAGE«ff»
IMPORT PROCEDURE PARSE
"===================="
               (STACKATTRIBUTESIZE, MAXSTACKATTRIBUTES: INTEGER;
                R4;  "ENTRY POINT OF SEMANTICS PROCEDURE
                R5;  "PARSE STACK BASE
                R7;  "PARSE TABLE PTR
                R6); "LINK
" THE PARSE PROCEDURE IS THE CONTROLLING PART OF THE PARSING SCHEME.
" AT ENTRY THE PARSE PROCEDURE STACKS THE OLD STATE IN THE FIRST PART
" OF THE PARSE TABLE (REFERENCED BY R7) AND ESTABLISHES AN INITIAL PARSE
" STATE FOR PARSING WITH THE ACTUAL PARSE TABLE.
" AT EXIT THE PARSER WILL REESTABLISH THE PARSE STATE AS IT WAS AT ENTRY,
" THUS ALLOWING DYNAMIC RESELECTION (STACKING AND UNSTACKING) OF PARSE
" TABLES.  HOWEVER, A SINGLE PARSE TABLE CANNOT BE USED RECURSIVELY.
" DURING EXECUTION THE PARSE PROCEDURE ACTIVATES THE SEMANTICS PROCEDURE
" (REFERENCED BY R4) IN THE FOLLOWING CASES:
"   R1:       R2:      R5:               COMMENTS:
"    1         -       PARSE STACK PTR   AN IDENTIFIER HAS BEEN SCANNED
"    2        VALUE    PARSE STACK PTR   A CONSTANT HAS BEEN SCANNED
"    3        SIZE     PARSE STACK PTR   A STRING HAS BEEN SCANNED
"    4        CAUSE     -                A PARSING ERROR HAS OCCURRED
"    N (>4)    -       PARSE STACK PTR   PRODUCTION NO 'N' IS RECOGNIZED
"                     (LEFT HAND SYMBOL)
" NOTE:  ALL REGISTERS MUST BE REESTABLISHED AT RETURN FROM THE SEMAN-
"        TICS PROCEDURE.

IMPORT VAR
  SYMBOLBUF: ARRAY [0..0] OF CHAR;
" WHENEVER AN IDENTIFIER OR A STRING IS RECOGNIZED BY THE PARSING SYSTEM,
" THE SYMBOL IS BUFFERED IN THE ARRAY 'SYMBOLBUF', TERMINATED BY TWO
" 'NULL' CHARACTERS.

" REQUIREMENTS:
" 
" IMPORT PROCEDURE IN_BYTE (R3 'CHARACTER VALUE(RETURN)'; R6 'LINK');
" DURING SCANNING (RECOGNITION OF SYMBOLS OF THE LANGUAGE), THE CHARACTERS
" ARE READ ONE BY ONE, BY CALLING THIS PROCEDURE.
"
" IMPORT VAR CHARCLASSTABLE: ARRAY [0..127] OF BYTE;
" THIS TABLE DEFINES THE CLASS AF EACH CHARACTER IN THE RANGE 0..127;
" CHARCLASS = (SKIP, ALFA, NUMERIC, DELIMITER, COMMENTCHAR, STRINGCHAR,
"              HEXCHAR, IGNORE, ESCAPE);