【编译原理】语法分析器

#define DeBUG
#include <iostream>
#include <cstring>
#include <cmath>
using namespace std ;

void yinzi(void);//因子
void biaodashi(void);//表达式
void yujuchuan(void);//语句串
void xiang(void);//项
void yuju(void);//语句
void lrparser(void);//分析函数
int scanner(void);//每次调用读取一个单词
int len;
int pre;
int sta;
int tlen;
int nowi;
int syn;
char token[1000];//临时存放单词
char PROGRAM[1000] = {0};//存放程序
bool isvar(char *s)
{
    int l = strlen(s);
    if (isdigit(s[0]))
        return false;
    for (int i = 0; i < l; i++)
    {
        if (isdigit(s[i]) || isalpha(s[i]))
            continue;
        else
            return false;
    }
    return true;
}
bool IsNum(char *s)
{
    int m = strlen(s);
    for (int i = 0; i < m; i++)
    {
        if (!isdigit(s[i]))
            return false;
    }
    return true;
}
bool iskong(char *s)
{
    int m = strlen(s);
    for (int i = 0; i < m; i++)
    {
        if (s[i] != ' ' || s[i] != '\n')
            return false;
    }
    return true;

}
int getnum(char *s)
{
    pre = sta;//状态切换
    if (IsNum(s))
        return 11;
    else  if (strcmp(s, "begin") == 0)return 1;
    else if (strcmp(s, "if") == 0)return 2;
    else if (strcmp(s, "then") == 0)return 3;
    else if (strcmp(s, "while") == 0)return 4;
    else if (strcmp(s, "do") == 0)return 5;
    else if (strcmp(s, "end") == 0)return 6;
    else if (isvar(s))          return 10;
    else if (strcmp(s, "+") == 0)return 13;
    else if (strcmp(s, "-") == 0)return 14;
    else if (strcmp(s, "*") == 0)return 15;
    else if (strcmp(s, "/") == 0)return 16;
    else if (strcmp(s, ":") == 0)return 17;
    else if (strcmp(s, ":=") == 0)return 18;
    else if (strcmp(s, "<") == 0)return 20;
    else if (strcmp(s, "<>") == 0)return 21;
    else if (strcmp(s, "<=") == 0)return 22;
    else if (strcmp(s, ">") == 0)return 23;
    else if (strcmp(s, ">=") == 0)return 24;
    else if (strcmp(s, "=") == 0)return 25;
    else if (strcmp(s, ";") == 0)return 26;
    else if (strcmp(s, "(") == 0)return 27;
    else if (strcmp(s, ")") == 0)return 28;
    else if (strcmp(s, "#") == 0)return 0;
    else if (s[0] == '/' && s[1] == '*')return -2;
    else return -1;
}
int  getsta(char c)
{
    if (isalpha(c))return 1;
    else if (isdigit(c)) return 2;
    else if (c == '(' || c == ')')return 33;
    else return 3;
}
int scanner()
{
    tlen = 0;
    memset(token, 0, sizeof(token));

    char ch;
    for (int i = nowi; i < len; i++, nowi++)
    {
        ch = PROGRAM[i];
        sta = getsta(ch);
        if (pre == -1)
        {
        }
        else if (pre == 1 && sta == 3)
        {
            return syn = getnum(token);
        }
        else if (pre == 2 && sta == 3)
        {
            return syn = getnum(token);
        }
        else if (pre == 3 && sta == 2)
        {
            if (!iskong(token))
                return syn = getnum(token);
        }
        else if (pre == 3 && sta == 1)
        {
            if (!iskong(token))
                return syn = getnum(token);
        }
        else if (pre == 33 || sta == 33)
        {
            if (!iskong(token))
                return syn = getnum(token);
        }
        if (ch != ' ' && ch != '\n')
            token[tlen++] = ch;
        pre = sta;
    }
    return syn = 0;
}
void init()
{
    int i = 0;
    while (scanf("%c", &PROGRAM[i]),PROGRAM[i]!='#')
    {
        i++;
    }
    len = strlen(PROGRAM);
    pre = -1;
    sta = 0;
    syn = -1;
    tlen = 0;
    nowi = 0;
    memset(token, 0, sizeof(token));
}
void xiang()
{
    yinzi();
    while (syn == 15 || syn == 16)
    {
        scanner();
        yinzi();
    }
    return ;
}
void biaodashi()
{
    xiang();
    while (syn == 13 || syn == 14)
    {
        scanner();
        xiang();
    }
    return ;
}
void yinzi()
{
    //scanner();
    if (syn == 10 || syn == 11)
    {
        scanner();
    }
    else if (syn == 27)
    {
        scanner();
        biaodashi();
        if (syn == 28)
        {
            scanner();
        }
        else
        {
            printf("error!:miss )\n");
        }
    }
    else
    {
        printf("error!:expression error!\n");
    }
}

void yuju()
{
    if (syn == 10)
    {
        scanner();
        if (syn == 18)
        {
            scanner();
            biaodashi();
        }
        else
        {
            printf("error!:miss :=\n");
        }
    }
    else
    {
        printf("error!:error variable\n");
    }
}
void yujuchuan()
{
    yuju();
    if(syn!=26)
        printf("error!:miss ;");
    while (syn == 26)
    {
        scanner();
        if (syn != 6)
            yuju();
    }

    return ;
}
void lrparser()
{
    if (syn == 1)
    {
        scanner();
        yujuchuan();
        if (syn == 6)
        {
            scanner();
            if (syn == 0)
                printf("success!\n");
            else
                printf("error!:error position of '#'\n");
        }
        else
            printf("error!:miss end or ;\n");
    }   
    else
    {
        printf("error!: miss begin\n");
    }
    return ;
}
int main()
{
#ifdef DeBUGs
    freopen("C:\\Users\\Sky\\Desktop\\1.in", "r", stdin);
#endif
    init();
    //printf("%s\n", PROGRAM);
    scanner();
    lrparser();
    // do
    // {
    //     scanner();
    //     printf("%d %s\n", syn, token);
    // }
    // while (syn != 0);

    return 0;
}
/*
begin 
x2:=9*(x-2);
x:=9;
x:=2*x+1/3;
end #
*/