abigen grammar

Modified BNF rules

This is the grammar for abigen files. The grammar is expressed in a modified BNF format.

A nonterminal symbol matches a sequence of other symbols, delimited by commas.

nonterminal = list , of , symbols ;

Some symbols are terminals, which are either in all caps or are in double quotes.

another-nonterminal = THESE , ARE , TERMINALS , AND , SO , IS , "this" ;

Alternation is expressed with a pipe.

choice = this | that | the-other ;

An option (zero or one) is expressed with parentheses.

optional = ( maybe , these ) , but , definitely , these ;

Repetition (zero or more) is expressed with parentheses and a star.

zero-or-more = ( list-part )* ;

The grammar

file is the starting symbol.

file = ( declaration )* , EOF ;

declaration = syscall-declaration ;

syscall-declaration = syscall IDENTIFIER attribute-list "(" parameter-list ")"
                      ( "returns" "(" type ( "," paramater-list ) ")" )

parameter-list = parameter | parameter "," parameter-list

parameter = IDENTIFIER ":" type attribute-list ( inout )

attribute-list = ( attribute )*

attribute = IDENTIFIER

type = IDENTIFIER

inout = "IN" | "OUT" | "INOUT"