12.16_实验四 递归下降语法分析程序设计
#include<stdio.h>
char curr;
char LL1[1000];
int N=0;
void scaner();
int digital(){ //panduanshifouweishuzi
if(curr >= '0' && curr <= '9')
{
return 1;
}
else {
return 0;
}
}
int english(){
if(curr >= 'a' && curr<='z' || curr >= 'A' && curr <= 'Z')
{
return 1;
}
else
return 0;
}
int yuansuanf(){
if(curr=='+'||curr=='-'||curr=='*'||curr=='/')
{
return 1;
}
else{
return 0;
}
}
int end(){
if(curr!='#'){
return 1;
}
else
return 0;
}
int check(){
if(digital()==1){
scaner();
if(end()==1){
if(yuansuanf()==1){
return 1;
}
else if(yuansuanf()==0){
return 0;
}
}
else if(end()==0){
return 1;
}
}
return 0;
}
void checking(){
int number;
qq: scaner();
if(digital()==1){
while(curr!='#'){
number=check();
if(number==1){
goto qq;
}
else if(number==0){
break;
}
}
}
if(number==1){
printf("没有错误
");
}
else
printf("%c
错误
",curr);
}
void main()
{ char ch;
int i=0;
printf("请输入需要分析的语法：(以#结束)
");
do{
scanf("%c",&ch);
LL1[i] = ch;
i++;
}while(ch != '#');
scaner();
checking();
}
void scaner(){ //用于读取源函数的下一个字符
N++;
if(LL1[N] == ' '){
N++;
}else
{
curr = LL1[N];
}
}