At some point, especially when there are lots of semantic actions attached
to various points, the grammar tends to be quite difficult to follow. In order
to keep an easy-to-read, consistent en aesthetically pleasing look to the Spirit
code, the following coding styleguide is advised.
This coding style is adapted and extended from the ANTLR/PCCTS style (Terrence
Parr) and Boost
coding guidelines (David Abrahams and Nathan Myers) and is the combined
work of Joel de Guzman, Chris Uzdavinis and Hartmut Kaiser.
- Rule names use std C++ (Boost) convention. The rule name may be very long.
- The '=' is neatly indented 4 spaces below. Like Boost, use spaces instead
- Breaking the operands into separate lines puts the semantic actions neatly
to the right.
- Semicolon at the last line terminates the rule.
- The adjacent parts of a sequence should be intended accordingly to have
all, what belongs to one level, at one indentation level.
= program_heading [heading_action]
>> block [block_action]
- Prefer literals in the grammar instead of identifiers. e.g. "program"
instead of PROGRAM, '>=' instead of GTE and
'.' instead of DOT. This makes it much easier to read. If
this isn't possible (for instance where the used tokens must be identified
through integers) capitalized identifiers should be used instead.
- Breaking the operands may not be needed for short expressions. e.g. *(','
>> file_identifier) as long as the line does not exceed 80 characters.
- If a sequence fits on one line, put spaces inside the parentheses to clearly
separate them from the rules.
>> *( ',' >> file_identifier )
- Nesting directives: If a rule does not fit on one line (80 characters)
it should be continued on the next line intended by one level.
- The brackets of directives, semantic expressions (using Phoenix or LL lambda
expressions) or parsers should be placed as follows.
alpha >> *(alnum | '_') [id_action]
- Nesting unary operators (e.g.Kleene star)
- Unary rule operators (Kleene star, '!', '+' etc.) should
be moved out one space before the corresponding indentation level, if this
rule has a body or a sequence after it, which does not fit on on line. This
makes the formatting more consistent and moves the rule 'body' at the same
indentation level as the rule itself, highlighting the unary operator.
= *( label_declaration_part
Copyright © 2001-2003 Joel de Guzman
Copyright © 2001-2002 Hartmut Kaiser
Copyright © 2001-2002 Chris Uzdavinis
Distributed under the Boost Software License, Version 1.0.
(See accompanying file LICENSE_1_0.txt or copy at