grammar HMKNF;

COMMENT: '#' .*? '\n' -> skip;
WS: [ \n\t\r]+ -> skip;

kb: (lrule | orule)*;

lrule: ((head body) | head | body) '.';
head: IDENTIFIER (',' IDENTIFIER)*;
body: ':-' (katom (',' katom)*)?;

orule: oformula '.';
oformula:
	'(' oformula ')'								# parenth
	| oatom											# literal
	| '-' oformula									# negation
	| oformula (operator = ('|' | '&')) oformula	# disjOrConj
	| <assoc = right> oformula '->' oformula		# imp;

katom: patom | natom;
oatom: IDENTIFIER;
patom: IDENTIFIER;
natom: 'not' IDENTIFIER;

IDENTIFIER: [a-z'][A-Za-z0-9'_]*;