#include<stdio.h>
#include<string.h>
char str[10];
int index=0;
void E(); //E->TX;
void X(); //X->+TX|-TX| e
void T(); //T->FY
void Y(); //Y->*FY |/fy| e
void F(); //F->(E) | id
int id(); //id
int main()
{
int len;
int m;
printf("请输入算数表达式：");
scanf("%s",str);
len=strlen(str);
str[len]='#';
str[len+1]='\0';
E();
printf("正确语句！\n");
strcpy(str,"");
index=0;
return 0;
}
void E()
T();
X();
void X()
if(str[index]=='+')
{
index++;
T();
X();
}
else if(str[index]=='-')
void T()
F();
Y();
void Y()
if(str[index]=='*')
F();
Y();
}
else if(str[index]=='/')
void F()
if(id())
else if (str[index]=='(')
{
if(str[index]==')')
{
index++;
}else{
printf("\n分析失败!\n");
exit (0);
}
else{
printf("分析失败!\n");
exit(0);
}
int id()
if(str[index]>='0'&&str[index]<='9')
while( str[index+1]>='0'&&str[index+1]<='9' )
index++;
if(str[index+1]>='a'&&str[index+1]<='z' )
return 0;
return 1;
else if(str[index]>='a'&&str[index]<='z' )
{
return 1;
}
else
return 0;