anchor.diff:  CLOSE : C L O S E;
   COBOL : C O B O L;
   CODE : C O D E;
  +CODEPAGE : C O D E P A G E;
   CODE_SET : C O D E MINUSCHAR S E T;
   COLLATING : C O L L A T I N G;
   COLUMN : C O L U M N;
  
positive.code: keyword : 
  	ACCEPT | ACCESS | ADD | ADDRESS | ADVANCING | AFTER | ALL | ALPHABET | ALPHABETIC | ALPHABETIC_LOWER | ALPHABETIC_UPPER | ALPHANUMERIC | ALPHANUMERIC_EDITED | ALSO | ALTER | ALTERNATE | AND | ANY | APOST | APPROXIMATE | ARE | AREA | AREAS | ARITH | AS | ASCENDING | ASCII | ASSIGN | AT | AUTHOR 
  	| BEFORE | BEGINNING | BINARY | BLANK | BLOCK | BOTTOM | BY 
  	| CALL | CANCEL | CD | CF | CH | CHANNEL | CHARACTER | CHARACTERS | CLASS | CLOCK_UNITS | CLOSE | COBOL | CODE | CODE_SET | COLLATING | COLUMN | COMMA | COMMITMENT | COMMON | COMMUNICATION | COMP | COMP_1 | COMP_2 | COMP_3 | COMP_4 | COMPUTATIONAL | COMPUTATIONAL_1 | COMPUTATIONAL_2 | COMPUTATIONAL_3 | COMPUTATIONAL_4 | COMPUTE | CONFIGURATION | CONTAINS | CONTENT | CONTINUE | CONTROL | CONTROLS | CONVERTING | COPY | CORR | CORRESPONDING | COUNT | CURRENCY | CURSOR 
  	| DATA | DATE | DATE_COMPILED | DATE_WRITTEN | DAY | DAY_OF_WEEK | DBCS | DE | DEBUG_CONTENTS | DEBUG_ITEM | DEBUG_LINE | DEBUG_NAME | DEBUG_SUB_1 | DEBUG_SUB_2 | DEBUG_SUB_3 | DEBUGGING | DECIMAL_POINT | DECLARATIVES | DEFINITION | DELETE | DELIMITED | DELIMITER | DEPENDING | DESCENDING | DESTINATION | DETAIL | DISABLE | DISK | DISPLAY | DISPLAY_1 | DIVIDE | DIVISION | DOWN | DUPLICATES | DYNAMIC 
  	| EBCDIC | EGCS | EGI | ELSE | EMI | ENABLE | END | END_ADD | END_CALL | END_COMPUTE | END_DELETE | END_DIVIDE | END_EVALUATE | END_IF | END_MULTIPLY | END_OF_PAGE | END_PERFORM | END_READ | END_RECEIVE | END_RETURN | END_REWRITE | END_SEARCH | END_START | END_STRING | END_SUBTRACT | END_UNSTRING | END_WRITE | ENDING | ENTER | ENTRY | ENVIRONMENT | EOP | EQUAL | ERROR | ESI | EVALUATE | EVERY | EXCEPTION | EXCLUSIVE | EXIT | EXTEND | EXTERNAL 
  	| FALSE | FD | FILE | FILE_CONTROL | FILLER | FINAL | FIRST | FOOTING | FOR | FROM | FULL | FUNCTION 
  
negative.code: // if statement
  
  ifStatement :
  	IF condition THEN? (statement* | NEXT SENTENCE)
  	(
  		ELSE (statement+ | NEXT SENTENCE)
  	)?
  