ot or_form I and_form I literal I bool_constant literal - bool_var I not( bool_var ) or_form - or( (and_form I literalf(2,1 ) and_form and( (or_form I literalf(2,1 ) The construct foo(x,) refers to x or more matches of foo (e.g. ( x I 10(2,1 is two or more items in sequences where each item is