rule_macros.h File Reference

DSL macros for defining grammar production rules. More...

This graph shows which files directly or indirectly include this file:

Go to the source code of this file.

Macros
#define	PREFIX_TK(tk)   TK_ ## tk
	See Name Mapping for Identifiers
#define	PREFIX_NT(nt)   NT_ ## nt
	See Name Mapping for Identifiers
#define	POSTFIX_NT_REST(nt)   nt ## _REST
	See Name Mapping for Identifiers
#define	EOA   -1
	Sentinel for end of alternative.
#define	EOP   -2
	Sentinel for end of production body.
#define	TK(tk)   { .ty = RDESC_TOKEN, .id = PREFIX_TK(tk) }
	Macro to create a terminal (token) production symbol.
#define	NT(nt)   { .ty = RDESC_NONTERMINAL, .id = PREFIX_NT(nt) }
	Macro to create a nonterminal production symbol.
#define	EPSILON   SEOA
	Epsilon production (empty/null production). Use to represent an empty alternative that matches nothing. This is equivalent to ε in BNF notation.
#define	r(...)   { { __VA_ARGS__, SEOA }, SEOP }
	Macro to define a grammar rule. Adds end of alternative and end of production body sentinels to grammar rules.
#define	ropt(...)    r(__VA_ARGS__ alt EPSILON)
	Macro to define an optional grammar rule (epsilon production).
#define	rrr(head, base, suffix)
	Defines right-recursive list rules. base and suffix parameters should wrapped with parenthesis (()).
#define	alt   , SEOA, }, {
	Separates grammar alternatives (alternative separator).

Detailed Description

DSL macros for defining grammar production rules.

Provides macros to define production rules in a more readable way.

Name Mapping for Identifiers

POSTFIX_NT_REST, PREFIX_TK, and PREFIX_NT macros determine how a raw token name passed to TK(X)/NT(X) is expanded into a C identifier (typically an enum member).

• Default: Identity mapping. PREFIX_TK(ID) expands to TK_ID, POSTFIX_NT(ID) to NT_ID, and POSTFIX_NT_REST(ID) to ID_REST.
• Override: Define this macro before including rule_macros.h to add namespaces (e.g., #define PREFIX_TK(x) MY_TK_ ## x).

Macro Definition Documentation

alt

#define alt   , SEOA, }, {

Separates grammar alternatives (alternative separator).

Expands to end-of-body sentinel and new alternative initialization.

Use between alternatives. For example, r(α alt β alt γ) is equivalent to α / β / γ, where / is ordered choice operator.

ropt

#define ropt

(

...

)

r(__VA_ARGS__ alt EPSILON)

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

This is a shortcut for a rule with two alternative: an alternative with the symbols provided and an empty (epsilon) one.

ropt(A, α) is equivalent to:

A → α / ε

For example, ropt(STMT, STMTS) defines:

<stmts> ::= <stmt> <stmts>
          / E

rrr

#define rrr	(		head,
			base,
			suffix
	)

Value:

        r(_rdesc_priv_trim_paren base, NT(POSTFIX_NT_REST(head))), \
        ropt(_rdesc_priv_trim_paren suffix, NT(POSTFIX_NT_REST(head)))

Defines right-recursive list rules. base and suffix parameters should wrapped with parenthesis (()).

Defines two nonterminals: the list head and its rest continuation. rrr(A, (β), (α)) is equivalent to:

A  → β A'
A' → α A' / ε

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

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

Warning

rrr(X, ...) expands into two production rules defining nonterminals NT_X and NT_X_REST. You must explicitly define NT_X_REST right after NT_X in your nonterminal enum definition. See Name Mapping for Identifiers.

Parameters

head	The base nonterminal.
base	The initial production sequence (beta).
suffix	The repeating production sequence (alpha).