#include<stdio.h>

#define id 1
#define equal 2
#define add 3

typedef struct token_s
{
    int type;
    char name[64];
} token_t;

token_t  token[100]= { {1, 'a'}, {2, '='},{1,'b'}, {3, '+' },{1,'b'}, {3, '+'},{1,'b'}};


int index=0;
token_t *gettoken()
{
    return &token[index];
}

token_t *getnext()
{
    index++;
    return &token[index];
}

int match_S()
{
    if(gettoken()->type==id&& getnext()->type == equal && match_A())
        printf("grammar right.\n");
    else printf("grammar wrong.\n");
}

int match_A()
{
    if(getnext()->type==id && match_B())
        return 1;
    else
        return 0;
}

int match_B()
{
    if(getnext()->type == add)
        if(match_A())
            return 1;
        else
            return 0;
    return 1;
}

int main()
{
    int i;
    for(i=0; i<100; i++){
        if(token[i].type != 0)
            printf("%s", token[i].name);
    }
    printf("\n");
    match_S();
}