Lexical Considerations

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Lexical Considerations

Case Insensitivity

Case does not matter in Theta. For example, "THEN", "then", and "Then" are all the same reserved word.

Tokens and Separators

A module is written as a sequence of tokens and separators. A token is a sequence of ``printing'' ASCII characters representing a reserved word, an identifier, a literal, an operator, or a punctuation symbol. A separator is a ``blank'' character (a space, vertical tab, horizontal tab, carriage return, newline, or form feed) or a comment. Zero or more separators may appear between any two tokens, where at least one separator is required between any two adjacent non-self-terminating tokens: reserved words, identifiers, integer literals, and real literals. Tokens are described in more detail in the following sections.


A comment begins with a percent sign ("with the first ``line-ending'' character (a vertical tab, carriage return, newline, or form feed). The enclosed characters serve as a single separator and are otherwise ignored by the compiler.