2.3.1 Numbers as Tokens

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 the next figure.

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 radix 10.                        
digit---a digit in the current input radix.                        

Figure 2-9. Syntax for Numeric Tokens

2.3.1.1 Potential Numbers as Tokens