simple query segmentation

%lex
%%
\s+ {}
(AND|OR)     { return 'LOG'; }
[a-zA-Z]+  { return 'VAR'; }
"("       return '('
")"      return ')'
"!"       return '!'
<<EOF>>   { return 'EOF'; }


/lex
%right '!'
%left 'LOG'
%start expressions
%%

expressions
  : exp EOF { return $exp }
  ;

exp :e|
  exp e {$$ = ['AND', $1, $2]};
e:
  '!' e {$$ = ['NOT', $2]}|
  e 'LOG' e { if($2.match(/^\s+$/)){$$ = ['AND', $1, $3]}else{$$ = [$2.trim(), $1, $3]}}|
  var {$$ = $var}|
  '(' e ')' { $$ = $2 };

var
  : VAR { $$ = yytext; }
  ;