#include <stdio.h>

include <stdlib.h>
include <ctype.h>
include <string.h>
define MAXTOKENS 100
define MAXTOKENLEN 64
enum type_tag{IDENTIFIER, QUALIFIER, TYPE}; /標識符，限定符，類型/
struct token{
    char type;
    char string[MAXTOKENLEN];
};
int top = -1;
struct token stack[MAXTOKENS];
struct token this;
define pop stack[top--]
define push(s) stack[++top] = s
define STRCMP(a,R,b) (strcmp(a,b) R 0)
/推斷標識符類型/
enum type_tag classify_string(void)
{
    char *s = this.string;
    if (STRCMP(s,==,"const"))
    {
        strcpy(s,"read-only");
        return QUALIFIER;
    }
    if (STRCMP(s,==,"volatile")) return QUALIFIER;
    if (STRCMP(s,==,"void")) return TYPE;
    if (STRCMP(s,==,"char")) return TYPE;
    if (STRCMP(s,==,"signed")) return TYPE;
    if (STRCMP(s,==,"unsigned")) return TYPE;
    if (STRCMP(s,==,"short")) return TYPE;
    if (STRCMP(s,==,"int")) return TYPE;
    if (STRCMP(s,==,"long")) return TYPE;
    if (STRCMP(s,==,"double")) return TYPE;
    if (STRCMP(s,==,"float")) return TYPE;
    if (STRCMP(s,==,"struct")) return TYPE;
    if (STRCMP(s,==,"union")) return TYPE;
    if (STRCMP(s,==,"enum")) return TYPE;
    return IDENTIFIER;
}
/讀取下一個標記到"this"可能讀入的字符包括：字母、數字、/
void gettoken(void)
{
    char *p = this.string;

/*略過空白字符*/
while((*p = (char)getchar()) == ' ') ;

/*是字母或數字*/
if (isalnum(*p))
{
    while(isalnum(*++p = (char)getchar())) ; /*讀到下一個不是字母或數字為止*/
    ungetc(*p,stdin);  /*將一個字符回退到輸入流*/
    *p = '';
    this.type = (char)classify_string();
    return;
}

if (*p == '*')
{
    strcpy(this.string,"pointer to");
    this.type = '*';
    return;
}

this.string[1] = '';
this.type = *p;
return;

}
/理解所有分析過程的代碼段/
int read_to_first_identifier(void)
{
    gettoken(); /取第一個標記/
    while(this.type != (char)IDENTIFIER) / 取到標識符終止，標識符未壓入棧 /
    {
        push(this);
        gettoken();
    }

printf("%s is ",this.string);
gettoken();/*再取標識符右邊一個符號*/
return 0;

}
int deal_with_arrays(void)
{
    while(this.type == '[')
    {
        printf("array ");
        gettoken();/數字域或']'/
        if (isdigit(this.string[0]))
        {
            printf("0..%d ",atoi(this.string)-1);
            gettoken(); /取']'/
        }

    gettoken(); /* 讀取']'后的下一個標記，可能還是一個'[' */
    printf("of ");
}

return 0;

}
int deal_with_function_args(void)
{
    while(this.type != ')') / 把函數參數取出來丟棄 /
    {
        gettoken();
    }

gettoken(); /* 讀取')'后的下一個標記 */
printf("function returning ");
return 0;

}
int deal_with_pointers(void)
{
    while(stack[top].type == '*')
    {
        printf("%s ",pop.string);
    }
    return 0;
}
int deal_with_declarator(void)
{
    /處理標識符后可能存在的數組或函數/
    switch(this.type)
    {
        case '[' : deal_with_arrays();break;
        case '(' : deal_with_function_args();break;
        default : break;
    }

deal_with_pointers(); /* 棧頂元素是'*' */

/*處理在讀到標識符之前壓入堆棧的符號*/
while(top >= 0)
{
    if (stack[top].type == '(')
    {
        pop;
        gettoken(); /* 讀取')'之后的符號，可能是'('或'[' */
        deal_with_declarator();  /* 遞歸調用 */
    }
    else
    {
        printf("%s ",pop.string);
    }
}

return 0;

}
int main(void)
{
    /將標記壓入堆棧中，直到遇見標識符/
    read_to_first_identifier();
    deal_with_declarator();
    printf("n");

return 0;

}</pre>