macros.ebnf

macro := '$syntax' [identifier] [integer] pattern '=' replacements ';' ;

(*
 NOTE: `'$'*FOO` means that `FOO` can be proceeded by any amount of `$`s.
 Likewise, `'$'+FOO` must be proceeded by at least one `$`
*)
pattern := '{' pattern-body '}' ;
pattern-body := pattern-sequence {'$|' pattern-sequence} ;
pattern-sequence := pattern-atom {pattern-atom};
pattern-atom
 := '$'+ident ':' pattern-kind
  | '$'*( pattern-body ')' (* note that non-`$` braces have to be matched *)
  | '$'*[ pattern-body ']'
  | '$'*{ pattern-body '}'
  | (? any non-macro token ?)
  ;
pattern-kind
 := '$'*	ident
  | '(' pattern-body ')'
  | '[' pattern-body ']'
  | '{' pattern-body '}' ;

replacements := '{' replacement-body '}'
replacement-body := replacement-atom {replacement-atom} ;
replacement-atom
 := '$'+ident
  | '$'+[ replacement-body ']'
  | '$'+( replacement-body ')'
  | '$'+{ replacement-body '}'
  | (? any non-macro token ?)
  ;