递归下降分析法

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#include<stdio.h>
char curr;
char YF[300];
int N=-1;

void T();
void E();
void F();
void e();
void t();
void error();
void scaner();

void main()
{ char ch;
int i=0;
printf("请输入需要分析的curr语法：(以#结束)\n");
do{
scanf("%c",&ch);
YF[i] = ch;
i++;
}while(ch != ‘#‘);
scaner();
E();
if(curr == ‘#‘)
printf("成功！\n");
else{
printf("文法有误！！\n");
error();
}

}

void scaner(){ 

N++;
if(YF[N] == ‘ ‘){
N++;
}else{
curr = YF[N];
}
}

void E(){
T();
e();
}
void T(){
F();
t();
}

void e(){
if(curr == ‘+‘){
scaner();
T();
e();
}
else if(curr == ‘-‘){
scaner();
T();
e();
}else if(YF[N+1] == ‘#‘ || YF[N+1] == ‘+‘ || YF[N+1] == ‘/‘ || YF[N+1] == ‘*‘ || YF[N+1] == ‘-‘){
if(YF[N] != ‘(‘ && YF[N] != ‘)‘)
error();
}
}

void t(){
if(curr == ‘*‘){
scaner();
F();
T();
}else if(curr == ‘/‘){
scaner();
F();
T();
}else if(YF[N+1] == ‘#‘ || YF[N+1] == ‘+‘ || YF[N+1] == ‘/‘ || YF[N+1] == ‘*‘ || YF[N+1] == ‘-‘){
if(YF[N] != ‘(‘ && YF[N] != ‘)‘)
error();
}
}
//LIE ZHI HUA TI GONG TAI MA
void F(){
if(curr == ‘(‘){
scaner();
E();
if(curr == ‘)‘){
scaner();
// printf("111111");
}else{
error();
}
}else{
while(1){
if(curr >= ‘a‘ && curr<=‘z‘ || curr >= ‘A‘ && curr <= ‘Z‘ || curr >= ‘0‘ && curr <= ‘9‘){
scaner();
}else{
break;
}
}
}
}

void error(){
printf("%d %c之后的文法有错！\n",N,curr);
}

递归下降分析法

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原文地址：http://www.cnblogs.com/huang123/p/5089274.html