When a token is read, it is interpreted as a number or symbol. The token is interpreted as a number if it satisfies the syntax for numbers specified in Figure 2–9.
numeric-token ::= !integer | !ratio | !float integer ::=[
sign]
{decimal-digit}^+ decimal-point |[
sign]
{digit}^+ ratio ::=[
sign]
{digit}^+ slash {digit}^+ float ::=[
sign]
{decimal-digit}* decimal-point {decimal-digit}^+[
!exponent]
|[
sign]
{decimal-digit}^+[
decimal-point {decimal-digit}*]
!exponent exponent ::= exponent-marker[
sign]
{digit}^+ sign—a sign. slash—a slash decimal-point—a dot. exponent-marker—an exponent marker. decimal-digit—a digit in radix10
. digit—a digit in the current input radix.
Figure 2–9: Syntax for Numeric Tokens