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#include<stdio.h>
#include<string.h>
#include<ctype.h>
#include<stdlib.h>
#define MAXTOKENS 100
#define MAXTOKENLEN 64
enum type_tag{IDENTIFIER,QUALIFIER,TYPE};
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
enum type_tag classify_string(void)
/*推断标示符的类型*/
{
char *s=this.string;
if(!strcmp(s,"const")){
strcmp(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,"float")) return TYPE;
if(!strcmp(s,"double")) return TYPE;
if(!strcmp(s,"struct")) return TYPE;
if(!strcmp(s,"union")) return TYPE;
if(!strcmp(s,"enum")) return TYPE;
return IDENTIFIER;
}
void gettoken(void) /*读取下一个标记"this"*/
{
char *p=this.string;
/*略过空白字符*/
while((*p=getchar())==' ');
if(isalnum(*p))
{
/* 读取的标识符以A-Z，0-9开头*/
while(isalnum(*++p=getchar()));
ungetc(*p,stdin);
*p='\0';
this.type=classify_string();
return;
}
if(*p=='*')
{
strcpy(this.string,"pointer to");
this.type='*';
return;
}
this.string[1]='\0';
this.type=*p;
return;
}
/*理解所有分析过程代码段*/
read_to_first_identifer()
{
gettoken();
while(this.type!=IDENTIFIER)
{
push(this);
gettoken();
}
printf("%s is ",this.string);
gettoken();
}
deal_with_arrays()
{
while(this.type=='[')
{
printf("array");
gettoken();
if(isdigit(this.string[0]))
{
printf("0..%d",atoi(this.string)-1);
gettoken();/*读取']'*/
}
gettoken();/*读取']'后的再一个标记*/
printf("of");
}
}
deal_with_function_args()
{
while(this.type!=')')
{
gettoken();
}
gettoken();
printf("function returning");
}
deal_with_pointers()
{
while(stack[top].type=='*')
{
printf("%s",pop.string);
}
}
deal_with_declarator()
{
/*处理标示符之后可能存在的数组/函数*/
switch(this.type)
{
case '[':deal_with_arrays();break;
case '(':deal_with_function_args();
}
deal_with_pointers();
/*处理在读入到标识符之前压入到堆栈中的符号*/
while(top>=0)
{
if(stack[top].type=='(')
{
pop;
gettoken();/*读取')'之后的符号*/
deal_with_declarator();
}
else
{
printf("%s",pop.string);
}
}
}
int main()
{
/*将标记压入堆栈中，直到遇见标识符*/
read_to_first_identifer();
deal_with_declarator();
printf("\n");
return 0;
}
