Lexical Conventions

• Comments are surrounded by { and }. The body of a comment may contain any characters except the end-of-comment character, so { this } } is not allowed. Comments can appear after any token.
• Comments should be treated as white space, along with spaces, tabs, carriage returns, and newlines.
• Keywords and identifiers must be surrounded by white space, non-alphanumeric tokens, or the beginning or end of the file.
• The class of lexemes for the token identifier is described by the regular expression l(l|d)*, where l stands for the set of uppercase and lowercase letters and d stands for the set of digits 0 through 9.
• Case is not significant.
• The regular expression for the token constant is d+(.d+|e)(E(+|-|e)d+|e) (notice the difference between the letter E and the symbol e; the latter is meant to stand for epsilon)
• The lexemes for relop are =, <>, <, >, <=, and >=. The lexemes for addop are +, -, and OR. The lexemes for mulop are *, /, DIV, MOD, and AND.