yacc文法規則加入字元變量名2

上一篇的字元變量都是一個字母的，這不夠用，需要支援單詞的變量

首先定義一個結構體，用來存儲符号和符号的值（可以實作一個哈希表，會比較快）

ch3hdr.h

#define NSYMS 20

struct symtable{
	char *name;
	double value;
}symtable[NSYMS];

extern struct symtable *symlook(char *s);
           

ch3hdr.c

#include "ch3hdr.h"
#include <string.h>
struct symtable *symlook(char *s)
{
	struct symtable *iterator = symtable;
	for(; iterator < &symtable[NSYMS]; iterator++){
		if (iterator->name && !strcmp(iterator->name, s)){
			return iterator;
		}
		if (!iterator->name){
			iterator->name = strdup(s);
			return iterator;
		}
	}
	yyerror("too many symbols");
	exit(1);
}
           

cal.y

%{
#include <stdio.h>
#include "ch3hdr.h"

%}
%union{
	double dval;
	struct symtable *symble;
}
%token PRINT
%token <symble> NAME
%token <dval> NUMBER

%type <dval> expression

%left '+' '-'
%left '*' '/'


%%
paragraph:
	paragraph statement '\n'
	|statement '\n'
	;
statement: 
	PRINT expression		{
								printf("\ntest yacc PRINT expression\n");
								printf("result is %lf", $2);
							}
	|NAME '=' expression 	{
								printf("\ntest yacc = expression\n");
								$1->value = $3;
							}
	;

expression: 
	expression '*' expression 	{
								printf("\ntest yacc expression + expression\n");
								$$ = $1 * $3;
							}
	|expression '/' expression 	{
								printf("\ntest yacc expression + expression\n");
								$$ = $1 / $3;
							}
	|expression '+' expression 	{
								printf("\ntest yacc expression + expression\n");
								$$ = $1 + $3;
							}
	|expression '-' expression 	{
								printf("\ntest yacc expression + expression\n");
								$$ = $1 - $3;
							}
	|NUMBER 				{
								printf("\ntest yacc NUMBER\n");
								$$ = $1;
							} 
	|NAME					{
								$$ = $1->value;
							}
	;

%%
           

cal.l

%{
#include "y.tab.h"
#include "ch3hdr.h"
#include <math.h>
%}
%%
print {printf("\ntest lex print\n"); return PRINT;}
[0-9]+ |
[0-9]*\.[0-9]+ {printf("\ntest lex NUMBER\n");yylval.dval = atof(yytext);  return NUMBER;}
[ \t] ;
[a-zA-Z][a-zA-Z0-9]*		{
								printf("\ntest lex %s", yytext);
								yylval.symble = symlook(yytext);
								return NAME;
							}
"$"  {return 0;}
\n |
. {printf("\ntest lex %s", yytext); return yytext[0];} 
%%
           

nosourcesmatoMacBook-Pro:~ nosources$ yacc -d cal.y && lex cal.l && cc -o cal y.tab.c lex.yy.c ch3hdr.c -ly -ll
           

variablename = 1+2*3-4*4

test lex variablename
test lex =
test lex NUMBER

test yacc NUMBER

test lex +
test lex NUMBER

test yacc NUMBER

test lex *
test lex NUMBER

test yacc NUMBER

test yacc expression + expression

test lex -
test yacc expression + expression

test lex NUMBER

test yacc NUMBER

test lex *
test lex NUMBER

test yacc NUMBER

test yacc expression + expression

test lex 

test yacc expression + expression

test yacc = expression
print variablename

test lex print

test lex variablename
test lex 

test yacc PRINT expression
result is -9.000000