### 7.1 Formal syntax

This section provides a formal syntax for Scheme written in an extended BNF.

All spaces in the grammar are for legibility. Case is insignificant; for example, ‘`#x1A`’ and ‘`#X1a`’ are equivalent. <empty> stands for the empty string.

The following extensions to BNF are used to make the description more concise: <thing>* means zero or more occurrences of <thing>; and <thing>+ means at least one <thing>.