📄 xlj.cpp
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#define N 100
#include<iostream.h>
#include<string.h>
#include<stdio.h>
static char a[N]; /*存放输入的语句*/
static char str[N]; /*存放构成单词符号的字符串*/
static int b[N];
static char copy[N][N];
static char ch;
static int i=0;
static int j=0;
static int m;
static int n;
int p;
int h[14][14];
int l[14][14];
struct list //定义结点
{
int data;
list *next;
};
class stack//定义栈类
{
private:
list *ptr;
public:
stack()
{ ptr=NULL;
}
void push(int i);
int pop();
};
void stack::push(int x)
{ list *q=new list;
q->data=x;
q->next=ptr;
ptr=q;
}
int stack:: pop()
{list *p;
int value;
value=ptr->data;
p=ptr;
ptr=ptr->next;
delete p;
return value;
}
//***************词法分析程序***********************
int word()
{
if((a[i]>=65&&a[i]<=90)||(a[i]>=97&&a[i]<=122))
{/* 识别标识符和关键字*/
ch=a[i];
str[j]=ch;
i++;
j++;
while((a[i]>=65&&a[i]<=90)||(a[i]>=97&&a[i]<=122 )||(a[i]>=48&&a[i]<=57))
{ch=a[i];
str[j]=ch;
i++;
j++;
}
if(a[i]!=' ')
i--;/*使i回调*/
if(strcmp(str,"if")==0||strcmp(str,"IF")==0)
return(2);
else if(strcmp(str,"then")==0||strcmp(str,"THEN")==0)
return(3);
else if(strcmp(str,"else")==0||strcmp(str,"ELSE")==0)
return(4);
else if(strcmp(str,"AND")==0||strcmp(str,"and")==0)
return(5);
else if(strcmp(str,"or")==0||strcmp(str,"OR")==0)
return(6);
else if(strcmp(str,"not")==0||strcmp(str,"NOT")==0)
return(7);
else return(1);
}
else if(a[i]>=48&&a[i]<=57)
{/*识别常数*/
ch=a[i];
str[j]=ch;
i++;
j++;
while((a[i]>=48&&a[i]<=57)&&i<N)
{
ch=a[i];
str[j]=ch;
i++;
j++;
}
if(a[i]!=' ')
i--;
return(8);
}
else if(a[i]=='<')
{ch=a[i];
str[j]=ch;
i++;
j++;
if(a[i]=='=')
{ch=a[i];
str[j]=ch;
return(10);
}
else
{ i--;
return(9);
}
}
else if(a[i]=='>')
{ch=a[i];
str[j]=ch;
i++;
j++;
if(a[i]=='=')
{ch=a[i];
str[j]=ch;
return(12);
}
else
{ i--;
return(11);
}
}
else if(a[i]=='!')
{ch=a[i];
str[j]=ch;
i++;
j++;
if(a[i]=='=')
{ch=a[i];
str[j]=ch;
return(13);
}
else
{ i--;
return(-1);
}
}
else if(a[i]=='=')
{ch=a[i];
str[j]=ch;
i++;
j++;
if(a[i]=='=')
{ch=a[i];
str[j]=ch;
return(15);
}
else
{ i--;
return(14);
}
}
else if(a[i]=='(')
{ch=a[i];
str[j]=ch;
return(17);
}
else if(a[i]==')')
{ch=a[i];
str[j]=ch;
return(18);
}
else if(a[i]==' ')
{
return(16);
}
else
return (-1);
}
int bn()
{ int k=0;
while(k<strlen(a))
{
b[n]=word();
if(b[n]==16)
{ i++;
k=i;
n--;
}
else if(b[n]!=-1)
{
i++;
k=i;
strcpy(copy[n],str);
cout<<str<<"<"<<b[n]<<">"<<" ";
}
else
{
cout<<endl;
cout<<"error！词法分析器分析到第"<<n+1<<"个单词符号这里发现错误！"<<endl;
return (-1);
break;
}
n++;
for(m=0;m<N;m++)
str[m]='\0';
j=0;
}
}
//*****************语法分析程序*******************
stack A,B;
void inserth(int i,int j)
{if(!h[i][j])
{
h[i][j]=1;
A.push(h[i][j]);
}
}
void insertl(int i,int j)
{if(!l[i][j])
{
l[i][j]=1;
B.push(l[i][j]);
}
}
int sentence_judge()
{
if(b[0]==2)
{
if(b[1]==1)
{
if(b[2]==3)
{
if(b[3]==1)
{
if(b[4]==14)
{
if(b[5]==8)
{
if(b[6]==4)
{
if(b[7]==1)
{
if(b[8]==14)
{
if(b[9]==8)
return (1);
else
return (-1);
}
else
return (-1);
}
else
return (-1);
}
else
return (-1);
}
else
return (-1);
}
else
return (-1);
}
else
return (-1);
}
else if((b[2]==9)||(b[2]==11)||(b[2]==15))
{
if(b[3]==1)
{
if(b[4]==3)
{
if(b[5]==1)
{
if(b[6]==14)
{
if(b[7]==8)
{
if(b[8]==4)
{
if(b[9]==1)
{
if(b[10]==14)
{
if(b[11]==8)
return (2);
else
return (-1);
}
else
return (-1);
}
else
return (-1);
}
else
return (-1);
}
else
return (-1);
}
else
return (-1);
}
else
return (-1);
}
else
return (-1);
}
else
return (-1);
}
else
return (-1);
}
else
return(-1);
}
else
return(-1);
}
void sentence()
{
char c[][N]={"S→if E then B else B","E→id1 A id2｜id1","A→<｜>｜==","B→id1=num"};
char d[][N]={"S","E","A","B","if","then","else","id1","id2","<",">","==","=","num"};//非终结符4个，终结符10个
char e[][N][N]={{"S","→","if","E","then","B","else","id1","=","num","#"},{"E","→","id1","A", "id2","｜","id1","#"},{"A","→","<","｜",">","｜","==","#"},{"B","→","id1","=","num","#"}};
int f[N][N];
int g[N][N];//存放关系，1代表＝关系，2代表<关系，3代表>关系
int k,n;
i=0;
g[1][5]=1;g[2][8]=1;
g[3][6]=1;g[4][2]=1;
g[4][7]=2;g[5][3]=1;
g[5][7]=2;g[6][3]=1;
g[6][7]=2;g[7][2]=1;
g[7][5]=3;g[7][9]=2;
g[7][10]=2;g[7][11]=2;
g[7][12]=1;g[8][5]=3;
g[9][8]=3;g[10][8]=3;
g[11][8]=3;g[11][13]=1;
g[13][6]=3;
cout<<"条件语句的文法如下："<<endl;
for(i=0;i<4;i++)
cout<<c[i]<<endl;
//**********求非终结符号的FIRST集和LAST集***************
for(j=0;j<4;j++)
{
for(i=0;i<4;i++)
{ if(strcmp(e[j][0],d[i])==0)
for(k=0;k<14;k++)
if(strcmp(e[j][2],d[k])==0)
inserth(i,k);
}
}
for(j=0;j<4;j++)
{
for(k=0;k<8;k++)
{
if(strcmp(e[j][k],"｜")==0)
{
for(i=0;i<4;i++)
{
if(strcmp(e[j][0],d[i])==0)
for(m=0;m<14;m++)
if(strcmp(e[j][k+1],d[m])==0)
inserth(i,k+1);
}
}
}
}
for(j=0;j<4;j++)
{
n=0;
while(strcmp(e[j][n],"#")!=0)
n++;
for(i=0;i<4;i++)
{ if(strcmp(e[j][0],d[i])==0)
for(k=0;k<14;k++)
{
if(strcmp(e[j][n-1],d[k])==0)
insertl(i,k);
}
}
}
for(j=0;j<4;j++)
{
for(k=0;k<8;k++)
{
if(strcmp(e[j][k],"｜")==0)
{
for(i=0;i<4;i++)
{
if(strcmp(e[j][0],d[i])==0)
for(m=0;m<14;m++)
if(strcmp(e[j][k-1],d[m])==0)
insertl(i,k-1);
}
}
}
}
//*******************利用FIRST集和LAST集求出优先关系****************************
for(j=0;j<4;j++)
{
for(i=2;i<10;i++)
{
if(strcmp(e[j][i],"｜")!=0&&strcmp(e[j][i+1],"｜")!=0&&strcmp(e[j][i+1],"#"))
{
for(k=0;k<14;k++)
if(strcmp(e[j][i],d[k])==0)
f[j][k]=1;
}
}
}
cout<<"构造简单优先关系表如下："<<endl;
cout<<" ";
for(i=0;i<14;i++)
cout<<d[i]<<" ";
cout<<endl;
cout<<d[0]<<endl;
cout<<d[1]<<" "<<"="<<endl;
cout<<d[2]<<" "<<"="<<endl;
cout<<d[3]<<" "<<"="<<endl;
cout<<d[4]<<" "<<"="<<" "<<"<"<<endl;
cout<<d[5]<<" "<<"="<<" "<<"<"<<endl;
cout<<d[6]<<" "<<"="<<" "<<"<"<<endl;
cout<<d[7]<<" "<<"="<<" "<<">"<<" "<<"<"<<" "<<"<"<<" "<<"<"<<" "<<"="<<endl;
cout<<d[8]<<" "<<">"<<endl;
cout<<d[9]<<" "<<">"<<endl;
cout<<d[10]<<" "<<">"<<" "<<"="<<endl;
cout<<d[11]<<" "<<">"<<endl;
cout<<d[12]<<endl;
cout<<d[13]<<" "<<">"<<endl;
if(sentence_judge()!=-1) //sentence_judge()进行规约
cout<<"输入的句子符合语法要求！";
else
cout<<"输入的句子不符合语法要求！";
}
//***********************中间代码生成，输出三地址码*******************************
void code()
{
if(sentence_judge()==1)
{
cout<<"L1: "<<"if "<<copy[1]<<" goto L2\n";
cout<<" goto L3\n";
cout<<"L2: "<<copy[3]<<copy[4]<<copy[5]<<"\n";
cout<<" goto Lnext\n"<<endl;
cout<<"L3: "<<copy[7]<<copy[8]<<copy[9]<<"\n";
cout<<" goto Lnext\n"<<endl;
cout<<"Lnext:\n"<<endl;
}
else
if(sentence_judge()==2)
{
cout<<"L1: if "<<copy[1]<<copy[2]<<copy[3]<<" goto L2\n";
cout<<" goto L3\n"<<endl;
cout<<"L2: "<<copy[5]<<copy[6]<<copy[7]<<"\n";
cout<<" goto Lnext\n"<<endl;
cout<<"L3: "<<copy[9]<<copy[10]<<copy[11]<<"\n";
cout<<" goto Lnext\n"<<endl;
cout<<"Lnext:\n "<<endl;
}
}
//******************************主函数*************************************
int main()
{
int value;
cout<<"--------IF THEN ELSE-------"<<endl;
cout<<"请输入条件语句："<<endl;
gets(a); /*输入一个句子*/
cout<<endl;
cout<<"词法分析分析出的单词及其对应的编码如下："<<endl;
value=bn();
cout<<endl<<endl;
if(value!=-1)
{
sentence();
}
cout<<endl;
if(sentence_judge()!=-1)
{
cout<<"进行语义分析输出的三地址码如下："<<endl;
code();
}
return 0;
}
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