Tokens

Tokens are a collection of classes used to represent elements of the VHDL language. They are grouped together under the vsg/tokens directory. Each file under vsg/tokens matches a VHDL production name. Each class in each file maps to an element in the VHDL production.

For example, the following production for the architecture_body:

architecture_body ::=
    architecture identifier of *entity*_name is
        architecture_declarative_part
    begin
        architecture_statement_part
    end [ architecture ] [ *architecture*_simple_name ] ;

has a file named vsg/tokens/architecture_body.py.

In the architecture_body.py file, the following classes exist:

• architecture_keyword

• identifier

• of_keyword

• entity_name

• is_keyword

• begin_keyword

• end_keyword

• end_architecture_keyword

• architecture_simple_name

• semicolon

The name of the class matches an item in the production with the following additional rules applied:

• All keywords have an _keyword suffix.

• All duplicately named keywords at the end of the production have an end_ prefix.

All classes in a production are extensions of base classes in the parser module.

production class	parser base class
architecture_keyword	parser.keyword
identifier	parser.identifier
of_keyword	parser.keyword
entity_name	parser.name
is_keyword	parser.keyword
begin_keyword	parser.keyword
end_keyword	parser.keyword
end_architecture_keyword	parser.keyword
architecture_simple_name	parser.simple_name
semicolon	parser.semicolon

Having a base class allows rules to be written against all types of a token, for example parser.semicolon. Extending base classes in the production allows for rules to be written against specific tokens in a production, for example architecture_body.semicolon.