1) Definitions of manifest constants = token types
2) Definitions based on REs are in the form:
Name_of_RE RE
•  Name_of_RE represents RE
• {Name_of_RE} is a reference to Name_of_RE
   used in other REs
Section I: Declaration
Example:
#define IF   256  /* constant for IF */
#define THEN 257  /* constant for THEN */
#define ID   258  /* constant for ID */
#define INT  259  /* constant for NUM */
letter [a-z]
digit [0-9]
id {letter}({letter}|{digit})*
integer {digit}+
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