A recursive-descent parser generator for D

LLtool generates the body of a parser from a context free grammar written in EBNF. The generated code fragment can be mixed into D source.

The generated code makes some assumptions about the environment:

• It assumes there are functions expect(), consume() and advance().
• It assumes there exists an enumeration TokenKind.
• It assumes there is a member/variable tok. The type of tok is not important. Only a member/property kind (of type TokenKind) is required.
• Currently the generator assumes that std.algorithm.among is imported.

The input for syntax LLtool is similar to yacc/bison. It has the following specification:

%token identifier, code, argument, string
%start lltool
%%
lltool : ( header )? ( rule )+ ;

header : ( "%start" identifier | "%token" tokenlist | "%eoi" identifier )* "%%" ;

tokenlist : tokendecl ("," tokendecl )* ;

tokendecl : (identifier | string) ( "=" identifier )? ;

rule : nonterminal "=" rhs "." ;

nonterminal : identifier ( argument )? ;

rhs : sequence ( "|" sequence )* ;

sequence : ( group | identifier ( argument)? | string | code | "%if" code )* ;

group : "(" rhs ( ")" | ")?" | ")*" | ")+" ) ;

This specification uses the following tokens:

• identifier: a sequence of letters and digits. First element must be a letter. Only ASCII characters are supported.
• string: an arbitrary sequence of characters, enclosed by " and " or ' and '.
• code: an arbitrary sequence of characters, enclosed by {. and .}.
• argument: an arbitrary sequence of characters, enclosed by < and > or <. and .>.

Single-line comments start with // and run until the end of line. Multi-line comments use /* and */ as delimiters. Multi-line comments may not be nested.

• Support parser generation at compile time
• Implement error recovery

Feedback of any kind is very much appreciated!