yacc.y

整理 unix v7 的 ya

/*
 * grammar for the input to Yacc
 * modified by mhss(http://mhss.nease.net)
 */

/* basic entities */
%token IDENTIFIER	/* includes identifiers and literals */
%token NUMBER	/* [0-9]+ */
%token C_IDENTIFIER	/* IDENTIFIER ':' */
%token TYPENAME	/* '<' IDENTIFIER '>' */

/*
 * reserved words:
 * %type => TYPEDEF, %nonassoc %binary => BINARY, %token %term => TERM  etc. 
 */
%token TERM LEFT RIGHT BINARY PREC TYPEDEF START UNION
%token MARK	/* the %% mark */
%token LCURLY	/* the %{ mark */

/* ascii character literals stand for themselves */

%start	spec

%%

spec
	:	defs MARK rules prog
	;

prog
	:	/* empty: the second MARK is optional */
	|	MARK
			{ /*In this action, eat up the rest of the file*/ }
	;

defs
	:	/* empty */
	|	defs def semicolons
	;

def
	:	START IDENTIFIER
	|	UNION
			{ /*Copy union definition to output*/ }
	|	LCURLY
			{ /*Copy C code to output file*/ }
	|	TYPEDEF TYPENAME tlist
	|	rword tag nlist
	;

rword
	:	TERM
	|	LEFT
	|	RIGHT
	|	BINARY
	;

tag
	:	/* empty */
	|	TYPENAME
	;

tlist
	:	tmno
	|	tlist tmno
	|	tlist ',' tmno
	;

nlist
	:	nmno
	|	nlist nmno
	|	nlist ',' nmno
	;

tmno
	:	IDENTIFIER
	;
	
nmno
	:	IDENTIFIER num
	;

num	:	/* empty */	
	|	NUMBER
	;

/*
 * rules section
 */

rules
	:	opt_declare C_IDENTIFIER rbody
	|	rules rule
	;

opt_declare
	:	/* empty */
	|	LCURLY
			{ /*Copy C code to output file*/ }
	;

rule
	:	C_IDENTIFIER rbody
	|	'|' rbody
	;

rbody
	:	rhs semicolons 
	|	rhs act semicolons 
	;
 
rhs
	:	/* empty */
	|	rhs prec
	|	rhs IDENTIFIER
	|	rhs act IDENTIFIER /* embedded action */
	;

act
	:	'='	/* automatically added on before '{' */
			{ /*Copy action, translate $$, etc.*/ }
	;

prec
	:	PREC IDENTIFIER
	;

semicolons
	:	/* empty */
	|	semicolons ';'
	;

%%