filter:		expression end_of_file { $return = $item[1] }
		|	{	$Persist::Filter::errors .= "ERROR: Could not parse filter.\n";
				foreach (@{$thisparser->{errors}}) {
					$Persist::Filter::errors .= "ERROR Line $_->[1]: $_->[0]\n";
				}
				$thisparser->{errors} = undef; }

end_of_file:
			/^\Z/

expression:	comparison logical_operator <commit> expression
			{ $return = new Persist::Filter::Junction(@item{qw(comparison logical_operator expression)}) }
		|	comparison 
		|	/not/i <commit> expression
			{ $return = new Persist::Filter::Not(lc($item[1]), $item{expression}) }
		|	<error?> <reject>

comparison:	first_operand <commit> comparison_operator second_operand
			{ $return = new Persist::Filter::Comparison(@item{qw(first_operand comparison_operator second_operand)}) }
		|	'(' <commit> expression ')' { $return = $item{expression} }
		|	<error?> <reject>

first_operand:	
			operand

second_operand:
			operand

operand:	identifier
		|	literal
		|	placeholder

logical_operator:	
			/and/i { $return = lc($item[1]) }
		|	/or/i { $return = lc($item[1]) }

comparison_operator:	
			'=' | '<>' | /<=?/ | />=?/
		|	/(?:not\s+)?i?like/i 
			{ $item[1] =~ s/\s+/ /; $return = lc($item[1]) }

identifier:	table_name '.' <commit> column_name 
			{ $return = new Persist::Filter::Identifier("$item{table_name}.$item{column_name}") }
		|	integer '.' <commit> column_name
			{ $return = new Persist::Filter::Identifier("$item{table_name}.$item{column_name}") }
		|	column_name
			{ $return = new Persist::Filter::Identifier($item{column_name}) }
		|	<error?> <reject>

table_name:	name

column_name:
			name

literal:	string
			{ $return = new Persist::Filter::String($item{string}) }
		|	number
			{ $return = new Persist::Filter::Number($item{number}) }

placeholder: '?'
			{ $return = new Persist::Filter::Placeholder('?') }

name:		/[a-z_][a-z0-9_]*/i

string:		"'" <commit> character(s) "'" { $return = "'".(join '', @{$item{'character(s)'}})."'" }
		|	<error?> <reject>

integer:	/\d+/

number:		/[+-]?[0-9]*\.[0-9]+(?:e[+-]?[0-9]+)?/i { $return = lc($item[1]) }
		|	/[+-]?[0-9]+\.?(?:e[+-]?[0-9]+)?/i { $return = lc($item[1]) }

character:	"\\\\'" { $return = "\\\\'" }
		|	/[^']/