3、若语句中有非英文字符，可能会导致程序崩溃。
测试数据：
const a=234,b="asdas",c=‘f‘,s=435.345;
sconst a=234,b="asdas",c=‘f‘,s=435.345;
const a=234,b="asdas",c=‘f‘,s=435.345
const a=234,b="asdas",c = ‘f‘ ,s =435.345;
const a=234,b="asdas",1c=‘f‘,s=435.345;
const a=234,_b="asdas",c=‘f‘,s=435.345;
const a=234,,b="asdas",c=‘f‘,s=435.345;
const a=0234,b="asdas",c=‘f‘,s=435.345;
const a=23ed4,b="asdas",c=‘f‘,s=435.345;
const a=234,b="asdas",c=‘ff‘,s=435.345;
const a=234,b="asdas",c=‘‘,s=435.345;
const a=234,b="",c=‘f‘,s=435.345;
const a=234,b="asdas",c=‘f‘,s=00.345;
const a=234,b="asdas",c=‘f‘,s=43sdf5.345;
const a=234,b="asdas",c=‘f‘,s=43.5.345;
测试结果:
const a=234,b="asdas",c=‘f‘,s=435.345;
@the constent is lagel ,fllow is the result of Analysis:
*********************************
a(int , 234)
b(String , "asdas")
c(char , ‘f‘)
s(float , 435.345)
num_int = 1 ;
num_float = 1 ;
num_char = 1 ;
num_string = 1 ;
*********************************
The Analysis is finish!
Please input a string again!
-------------------------------------------------
sconst a=234,b="asdas",c=‘f‘,s=435.345;
It is not a constant declaration statement! <const>
The Analysis is finish!
Please input a string again!
-------------------------------------------------
const a=234,b="asdas",c=‘f‘,s=435.345
It is not a constant! <;>
The Analysis is finish!
Please input a string again!
-------------------------------------------------
const a=234,b="asdas",c = ‘f‘ ,s =435.345;
@the constent is lagel ,fllow is the result of Analysis:
*********************************
a(int , 234)
b(String , "asdas")
c(char , ‘f‘)
s(float , 435.345)
num_int = 1 ;
num_float = 1 ;
num_char = 1 ;
num_string = 1 ;
*********************************
The Analysis is finish!
Please input a string again!
-------------------------------------------------
const a=234,b="asdas",1c=‘f‘,s=435.345;
<1c>: the name is illege!
The Analysis is finish!
Please input a string again!
-------------------------------------------------
const a=234,_b="asdas",c=‘f‘,s=435.345;
<_b>: the name is illege!
The Analysis is finish!
Please input a string again!
-------------------------------------------------
const a=234,,b="asdas",c=‘f‘,s=435.345;
<,b>: the name is illege!
The Analysis is finish!
Please input a string again!
-------------------------------------------------
const a=0234,b="asdas",c=‘f‘,s=435.345;
<0234> :is not a legal int! <0>
The Analysis is finish!
Please input a string again!
-------------------------------------------------
const a=23ed4,b="asdas",c=‘f‘,s=435.345;
<23ed4> :is not a legal int! <other charecater>
The Analysis is finish!
Please input a string again!
-------------------------------------------------
const a=234,b="asdas",c=‘ff‘,s=435.345;
<‘ff‘> :is not a legal charThe Analysis is finish!
Please input a string again!
-------------------------------------------------
const a=234,b="asdas",c=‘‘,s=435.345;
<‘‘> :is not a legal charThe Analysis is finish!
Please input a string again!
-------------------------------------------------
const a=234,b="",c=‘f‘,s=435.345;
<""> :is not a legal StringThe Analysis is finish!
Please input a string again!
-------------------------------------------------
const a=234,b="asdas",c=‘f‘,s=00.345;
<00.345> :is not a legal float! <00>
The Analysis is finish!
Please input a string again!
-------------------------------------------------
const a=234,b="asdas",c=‘f‘,s=43sdf5.345;
<43sdf5.345> :is not a legal float! <other charecater>
The Analysis is finish!
Please input a string again!
-------------------------------------------------
const a=234,b="asdas",c=‘f‘,s=43.5.345;
<43.5.345> :is not a legal float! <.. >
The Analysis is finish!
Please input a string again!
-------------------------------------------------
/*
@常量定义语法判断
@作者：Amy
@版本：1.1
*/
#include<iostream>
#include<string>
#include<vector>
#include<stdio.h>
#include<string.h>
#include<ctype.h>
using namespace std;
struct node //常量定义分析
{
string name; //常量名
string in; //常量内容
string type; //常量类型//interger，char,int,float
}content;
string s,ss;
vector<node> ve;
int len;
int num_int,num_float,num_char,num_string;
char a[1000];
bool initial()//初始化,输入数据
{
num_int=0;
num_float=0;
num_char=0;
num_string=0;
ve.clear();
if(gets(a))
{
s=a;
return true;
}
return false;
}
bool judge_const()//判断const是否正确
{
int x=s.find(" ",0);
ss=s.substr(0,x);//提取关键字const
for(int i=0;i<s.size();i++) //去掉空格
if(s[i]==‘ ‘)s.erase(i--,1);
s.copy(a,s.size()-5,5);
len=s.size()-5;
a[len]=‘\0‘;
if(ss!="const")return false;
return true;
}
bool jundge_tail() //判断是否有“；”
{
if(a[len-1]!=‘;‘)return false;
return true;
}
void sent()//提取语句（每个定义）
{
int side=0;
char name1[20],in[20];
a[len-1]=‘,‘;
while(sscanf(a+side,"%[^=]%[^,]",name1,in))
{
content.name=name1;
content.in=in;
content.in.erase(0,1);
ve.push_back(content);
side+=strlen(name1)+strlen(in)+1;
if(side==len) //到结尾
break;
}
}
bool judge_name() //判断常量名是否合语法
{
for(int i=0;i<ve.size();i++)
if(!isalpha(ve[i].name[0])){ //首字符不是字母
cout<<"<"<<ve[i].name<<">";
return false;
}
return true;
}
void classf() //根据常量特征分类
{
for(int i=0;i<ve.size();i++){
if(ve[i].in[0]==‘"‘) //双引号开始的是字符串
ve[i].type="String",num_string++;
else if(ve[i].in[0]==‘\‘‘) //单引号开始的是字符
ve[i].type="char",num_char++;
else if(ve[i].in.find(".",0)<ve[i].in.size()) //带小数点的是小数
ve[i].type="float",num_float++;
else ve[i].type="int",num_int++; //否则是整数
}
}
bool judge_content()//判断常量内容是否正确
{
char txt[20];
for(int i=0;i<ve.size();i++){
if(ve[i].type=="int"){
ve[i].in.copy(a,ve[i].in.size(),0);
a[ve[i].in.size()]=‘\0‘;
if(sscanf(a,"%[0-9]",txt)&&strlen(a)==strlen(txt)); //整数中没有非数字字符
else
{
cout<<"<"<<ve[i].in<<"> :is not a legal int! <other charecater>"<<endl;
return false;
}
if(ve[i].in[0]==‘0‘){ //整数不能前导零
cout<<"<"<<ve[i].in<<"> :is not a legal int! <0>"<<endl;
return false;
}
}
if(ve[i].type=="float"){
ve[i].in.copy(a,ve[i].in.size(),0);
a[ve[i].in.size()]=‘\0‘;
if(sscanf(a,"%[0-9,.]",txt)&&strlen(a)==strlen(txt)); //小数中没有非数字和非小数点的字符
else
{
cout<<"<"<<ve[i].in<<"> :is not a legal float! <other charecater>"<<endl;
return false;
}
if(ve[i].in[0]==ve[i].in[1]&&ve[i].in[1]==‘0‘){ //小数不能前导两个零
cout<<"<"<<ve[i].in<<"> :is not a legal float! <00>"<<endl;
return false;
}
if(ve[i].in.find(".",ve[i].in.find(".",0)+1)<ve[i].in.size()){//小数中不能有多个小数点
cout<<"<"<<ve[i].in<<"> :is not a legal float! <.. >"<<endl;
return false;
}
}
if(ve[i].type=="char"){
if(ve[i].in.size()!=3){
cout<<"<"<<ve[i].in<<"> :is not a legal char";//常量中自能有一个字符
return false;
}
}
else {
if(ve[i].in.size()<3){//字符串常量中不能为空
cout<<"<"<<ve[i].in<<"> :is not a legal String";
return false;
}
}
}
return true;
}
void output()//输出结果，若无语法问题
{
cout<<"@the constent is lagel ,fllow is the result of Analysis:";
cout<<"\n*********************************\n";
for(int i=0;i<ve.size();i++)
cout<<ve[i].name<<"("<<ve[i].type<<" , "<<ve[i].in<<")"<<endl;
cout<<endl;
cout<<"num_int = "<<num_int<<" ;\n";
cout<<"num_float = "<<num_float<<" ;\n";
cout<<"num_char = "<<num_char<<" ;\n";
cout<<"num_string = "<<num_string<<" ;\n";
cout<<"\n*********************************\n";
}
int main()
{
bool x;
while(initial())
{
if(!judge_const())//判断是否有关键字“const”
{
cout<<"It is not a constant declaration statement! <const>"<<endl;
goto end1;
}
if(!jundge_tail())//判断句尾是否有“；”
{
cout<<"It is not a constant! <;>"<<endl;
goto end1;
}
sent();
if(!judge_name())//判断常量名是否合法
{
cout<<": the name is illege!\n\n";
goto end1;
}
classf(); //分析常量类型
if(!judge_content()) //判断常量初始化是否有误
goto end1;
output(); //输出结果（若没有发现问题）
end1:
cout<<"The Analysis is finish!\nPlease input a string again!"<<endl;
cout<<"\n-------------------------------------------------\n"<<endl;
}
return 0;
}
编译原理_常量定义语句语法分析,布布扣,bubuko.com
原文：http://blog.csdn.net/huahua520amy/article/details/20937867