bnf_dsl.h File Reference

Macros for context-free grammar definitions. More...

#include <stddef.h>

Go to the source code of this file.

Macros
#define	PREFIX_TK(tk)   tk
	Name mapping for token identifiers.
#define	PREFIX_NT(nt)   nt
#define	POSTFIX_NT_REST(nt)   nt ## _REST
	Name mapping for non-terminal list to rest types.
#define	EOB   -1
#define	EOC   -2
#define	SEOB   { .ty = CFG_SENTINEL, .id = EOB }
	Sentinel struct for the end of a rule's body (EOB)
#define	SEOC   { { .ty = CFG_SENTINEL, .id = EOC } }
	Sentinel struct for the end of a construct's variants (EOC)
#define	TK(tk)   { .ty = CFG_TOKEN, .id = PREFIX_TK(tk) }
	Macro to create a terminal (token) production symbol.
#define	NT(nt)   { .ty = CFG_NONTERMINAL, .id = PREFIX_NT(nt) }
	Macro to create a non-terminal production symbol.
#define	EPSILON   SEOB
	Macro to create an epsilon production symbol.
#define	r(...)   { { __VA_ARGS__ SEOB }, SEOC }
	Macro to define a grammar rule. Adds end-of-body and construct sentinels to grammar rules.
#define	rrr(head, listelem, delim)
	Macro to define a pair of rules for a right-recursive list.
#define	ropt(...)   { { __VA_ARGS__, SEOB }, { SEOB }, SEOC }
	Macro to define an optional grammar rule (epsilon production).
#define	alt   SEOB, }, {
	Macro for syntactic sugar to separate non-terminal alternatives.

Detailed Description

Macros for context-free grammar definitions.

Provides macros (r, rrr, ropt) to define these production rules in a readable way.

You may define PREFIX_TK and PREFIX_NT macros before including this file to automatically add prefixes in grammar definitions.

Macro Definition Documentation

alt

#define alt   SEOB, }, {

Macro for syntactic sugar to separate non-terminal alternatives.

Expands to the end-of-body sentinel and new variant syntax.

EOB

#define EOB   -1

integer representing EOB (end-of-body)

EOC

#define EOC   -2

integer representing EOC (end-of-construct)

PREFIX_NT

#define PREFIX_NT

(

nt

)

nt

See also

PREFIX_TK

PREFIX_TK

#define PREFIX_TK

(

tk

)

tk

Name mapping for token identifiers.

This macro determines how a raw token name passed to TK(...) is expanded into a C identifier (typically an enum member).

• Default: Identity mapping. TK(IDENT) expands to IDENT.
• Override: Define this macro before including the DSL to add namespaces (e.g., #define PREFIX_TK(x) MY_TK_ ## x).

ropt

#define ropt

(

...

)

{ { __VA_ARGS__, SEOB }, { SEOB }, SEOC }

Macro to define an optional grammar rule (epsilon production).

This is a shortcut for a rule with two variants:

1. The symbols provided in __VA_ARGS__
2. An empty (epsilon) production

rrr

#define rrr	(		head,
			listelem,
			delim
	)

Value:

    { { listelem, NT(POSTFIX_NT_REST(head)), SEOB }, SEOC }, \
    { { delim, NT(head), SEOB }, { SEOB }, SEOC }

Macro to define a pair of rules for a right-recursive list.

This is the standard pattern for lists and operator precedence. It automatically defines the rule for 'head' and 'head_REST'.

For example, rrr(EXPR_LS, NT(EXPR), TK(COMMA)) defines:

1. <expr_ls> ::= <expr> <expr_ls_rest>
2. <expr_ls_rest> ::= "," <expr_ls> | E

Parameters

head	The base non-terminal.
listelem	The non-terminal for the list element.
delim	The token used as a separator.

SEOB

#define SEOB   { .ty = CFG_SENTINEL, .id = EOB }

Sentinel struct for the end of a rule's body (EOB)

Usage with DSL is not recommended, use EPSILON instead.

SEOC

#define SEOC   { { .ty = CFG_SENTINEL, .id = EOC } }

Sentinel struct for the end of a construct's variants (EOC)

Not recommended, use r and ropt instead.