What is wrong with this simple example?

[Peng Yu]

I try to run the example on
http://tldp.org/HOWTO/Lex-YACC-HOWTO-4.html. But I get the following
error. Could somebody let me know what I am wrong?

$ bison -d example4.y
example4.y:24.1-8: syntax error, unexpected identifier:
$ cat example4.y
%{
#include <stdio.h>
#include <string.h>

void yyerror(const char *str)
{
        fprintf(stderr,"error: %s\n",str);
}

int yywrap()
{
        return 1;
}

main()
{
        yyparse();
}

%}

%token NUMBER TOKHEAT STATE TOKTARGET TOKTEMPERATURE

commands: /* empty */
        | commands command
        ;

command:
        heat_switch
        |
        target_set
        ;

heat_switch:
        TOKHEAT STATE
        {
                printf("\tHeat turned on or off\n");
        }
        ;

target_set:
        TOKTARGET TOKTEMPERATURE NUMBER
        {
                printf("\tTemperature set\n");
        }
        ;