sigma= { +, -, *, /, ^, (, ), numero, ; } linea::= expr ; expr::= term B | + term B | - term B B::= +term B | -term B | term:: factor C C:= *factor | /factor | factor::= prim E E::= ^ F | F::= prim E prim::= numero | (expr) ======================================== U:= term | + term | - term expr::= U { + term | - term } term ::= factor { * factor | / factor }