Editing Lexical analysis (section)

=== Off-side rule ===
{{further|Off-side rule}}
The [[off-side rule]] (blocks determined by indenting) can be implemented in the lexer, as in [[Python (programming language)|Python]], where increasing the indenting results in the lexer emitting an INDENT token and decreasing the indenting results in the lexer emitting one or more DEDENT tokens.<ref>{{cite web |title=Lexical analysis > Indentation |url=https://docs.python.org/3.11/reference/lexical_analysis.html#indentation |website=The Python Language Reference |access-date=21 June 2023}}</ref> These tokens correspond to the opening brace <code>{</code> and closing brace <code>}</code> in languages that use braces for blocks and means that the phrase grammar does not depend on whether braces or indenting are used. This requires that the lexer hold state, namely a stack of indent levels, and thus can detect changes in indenting when this changes, and thus the lexical grammar is not [[Context-free grammar|context-free]]: INDENT–DEDENT depend on the contextual information of prior indent levels.