📄 ifelse.cpp
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#include <iostream>
#include <iomanip>
#include <fstream>
#include <string>
#include <cctype>
using namespace std;
//------------------------------创建全局成员，声明函数-----------------------------------------------------
struct Node{
int type;//保存单词种类
char data[20]; //保存单词
Node* next; //指向下一单词
};
char words[10]; //保存变量 数字
static int k=0;
Node* head;
char str[256];
ifstream fin("example.txt",ios::in);
int bound(char ch);
int bSym(char ch);
char* copy(Node* p,Node* top);
int count(Node* p,Node* q);
void print_evalue(Node* p,Node* q);
Node* findE(Node* s);
Node* findE_1(Node* s);
char *findG(char *str);
char getC();
int grammar(Node* s);
void init();
void init_gene();
void initMatrix();
int location(Node* p);
int mSym(char ch);
void nSym(char ch);
int oper(char ch);
int operSym(char ch);
char Precede (char op1,char op2);
void print_link(Node *head);
void printE(Node* p,Node* q);
void print_result(Node* s);
int WordAnalysis();
char wordtypeE(Node* s) ;
//----------------------------------------主函数-----------------------------------------------------
int main()
{
int i;
init();
//cout<<"词法分析结果如下"<<endl;
i=WordAnalysis();
if(i==1)
{
i=grammar(head->next);
if(i==1)
{
cout<<"四元式输出:"<<endl;
print_result(head->next);
}
else return 0;
}
else return 0;
return 0;
}
//----------------------------------------------函数部分----------------------------------------------
//------------------------------------词法分析--------------------------------------------------
void init() //初始化文件
{
int i=0;
char ch;
fin.get(ch);
do
{
if((ch!=' ')&&(ch!='\n')){
str[i++]=ch;
}
else
{ fin.get(ch);
continue;
}
fin.get(ch);
}while(!fin.eof());
/*while(!fin.eof()){
fin.get(ch);
if((ch!=' ')&&(ch!='\n')){
str[i++]=ch;
}
else continue;
}*/
str[i]='#';
cout<<"输入的语句如下:"<<endl;
cout<<str<<endl;
}
char getC(){
char ch=str[k+1]; //取下一字符
k++;
return ch;
}
int mSym(char ch){ //标识符
int i=0;
while(isalpha((int)ch)||isdigit((int)ch)||ch=='_')
{
words[i]=ch;
words[i+1]='\0';
if(!strcmp(words,"if"))
{
k++;
return 3;
}
if(!strcmp(words,"else"))
{
k++;
return 3;
}
if(!strcmp(words,"then"))
{
k++;
return 3;
}
ch=getC();
i++;
}
return 1;
}
void nSym(char ch){ //数字
int i=0;
while(isdigit((int)ch)){
words[i]=ch;
words[i+1]='\0';
ch=getC();
i++;
}
}
int oper(char ch){
if(ch=='+'||ch=='-'||ch=='*'||ch=='/') return 1;
else if(ch=='<'||ch=='>'||ch=='='||ch=='!') return 2;
else if(ch=='&'||ch=='|') return 3;
return 0;
}
int operSym(char ch){
if(oper(ch)==1){
words[0]=ch;
words[1]='\0';
ch=getC();
if(words[0]=='+'){
if(ch=='+'){
words[1]=ch;
words[2]='\0'; //cout<<words<<endl;
k++;
return 12;
}
}
if(words[0]=='-'){
//ch=getC();
if(ch=='-'){
words[1]=ch;
words[2]='\0'; //cout<<words<<endl;
k++;
return 12;
}
}
return 11;
}
if(oper(ch)==2){
words[0]=ch;
words[1]='\0';
ch=getC();
if(words[0]=='<'){
//ch=getC();
if(ch=='='){
words[1]=ch;
words[2]='\0';
k++;
return 22;
}
}
if(words[0]=='>'){
//ch=getC();
if(ch=='='){
words[1]=ch;
words[2]='\0';
k++;
return 22;
}
}
if(words[0]=='!'){
//fin.get(ch);
if(ch=='='){
words[1]=ch;
words[2]='\0';
k++;
return 22;
}
if(ch!='=') return 31;
}
if(words[0]=='='){
//fin.get(ch);
if(ch=='='){
words[1]=ch;
words[2]='\0';
k++;
return 22;
}
if(ch!='=') return 4;
}
return 21;
}
if(oper(ch)==3){
words[0]=ch;
words[1]='\0';
ch=getC();
if(words[0]=='&'){
//fin.get(ch);
if(ch=='&'){
words[1]=ch;
words[2]='\0';
k++;
return 32;
}
}
if(words[0]=='|'){
//fin.get(ch);
if(ch=='|'){
words[1]=ch;
words[2]='\0';
k++;
return 32;
}
}
return 0;
}
//fin.get(ch);
//return 0;
}
int bound(char ch){
if(ch=='('||ch==')'||ch=='{'||ch=='}'||ch==';'||ch=='#')
return 1;
return 0;
}
int bSym(char ch){
int i=0;
words[i]=ch;
words[i+1]='\0';
k++;
if(words[0]=='('||words[0]==')') return 51;
if(words[0]=='{'||words[0]=='}') return 52;
if(words[0]=='#') return 0;
return 53;
}
int WordAnalysis()
{
char ch;
int i,j;
// cout<<"单词种别：#----0, 标识符----1，常数----2，关键字----3，运算符----4，界符----5"<<endl;
// cout<<" 算术运算符----41, 关系运算符----42, 逻辑运算符----43, 赋值运算符----44"<<endl;
//Node *head;
head=new Node;//可以改到主函数中
head->next=NULL;
Node *p,*q;
p=head;
//fin.get(ch); //cout<<ch<<endl;
do{
for(j=0;j<10;j++)
words[j]='\0';
ch=str[k]; //cout<<ch<<endl;
if(isalpha((int)ch)||ch=='_'){
i=mSym(ch);
q=new Node;
q->type=i;
strcpy(q->data,words); //cout<<q->data<<endl;
q->next=NULL;
if(head->next==NULL){
head->next=q;
p=q;
}
else{
p->next=q;
p=q;
}
}
else if(isdigit((int)ch)){
nSym(ch);
q=new Node;
q->type=2;
strcpy(q->data,words); //cout<<q->data<<endl;
q->next=NULL;
if(head->next==NULL){
head->next=q;
p=q;
}
else{
p->next=q;
p=q;
}
}
else if(oper(ch)){
//operSym();
q=new Node;
i=operSym(ch);
if(i==11) q->type=411;
if(i==12) q->type=412;
if(i==21) q->type=421;
if(i==22) q->type=422;
if(i==31) q->type=431;
if(i==32) q->type=432;
if(i==4) q->type=44;
if(i==0)
{
cout<<"词法分析错误!"<<endl;
return 0;
}
strcpy(q->data,words); //cout<<q->data<<endl;
q->next=NULL;
if(head->next==NULL){
head->next=q;
p=q;
}
else{
p->next=q;
p=q;
}
}
else if(bound(ch)){
q=new Node;
i=bSym(ch);
if(i==51) q->type=51;
if(i==52) q->type=52;
if(i==53) q->type=53;
if(i==0) q->type=0;
strcpy(q->data,words); //cout<<q->data<<endl;
q->next=NULL;
if(head->next==NULL){
head->next=q;
p=q;
}
else{
p->next=q;
p=q;
}
}
else
{
cout<<"词法分析错误"<<endl;
return 0;
}
}while(ch!='#');
//print_link(head);
return 1;
}
void print_link(Node *head){
Node *r;
r=head->next;
while(r->next){
cout<<setiosflags(ios::left)<<setw(6)<<r->type<<" "<<r->data<<endl;
r=r->next;
}
cout<<setiosflags(ios::left)<<setw(6)<<r->type<<" "<<r->data<<endl;
}
//--------------------------------词法分析结束-------------------------------------------------------
//----------------------------------语法分析-------------------------------------------------------
struct Ge
{//表示产生式
char left[2];//左部
char right[14];//右部
};
Ge gene[16];
void init_gene(){
strcpy(gene[0].left,"S");
strcpy(gene[0].right,"ifBthenAelseA");
strcpy(gene[1].left,"B");
strcpy(gene[1].right,"i<E");
strcpy(gene[2].left,"B");
strcpy(gene[2].right,"i<=E");
strcpy(gene[3].left,"B");
strcpy(gene[3].right,"i==E");
strcpy(gene[4].left,"B");
strcpy(gene[4].right,"i!=E");
strcpy(gene[5].left,"B");
strcpy(gene[5].right,"i>=E");
strcpy(gene[6].left,"B");
strcpy(gene[6].right,"i>E");
strcpy(gene[7].left,"A");
strcpy(gene[7].right,"i=E");
strcpy(gene[8].left,"E");
strcpy(gene[8].right,"T+E");
strcpy(gene[9].left,"E");
strcpy(gene[9].right,"T-E");
strcpy(gene[10].left,"E");
strcpy(gene[10].right,"T");
strcpy(gene[11].left,"T");
strcpy(gene[11].right,"T*F");
strcpy(gene[12].left,"T");
strcpy(gene[12].right,"T/F");
strcpy(gene[13].left,"T");
strcpy(gene[13].right,"F");
strcpy(gene[14].left,"F");
strcpy(gene[14].right,"i");
strcpy(gene[15].left,"F");
strcpy(gene[15].right,"n");
}
char Matrix[23][23];
void initMatrix() //--------简单优先关系矩阵---------------
{
int i,j;
for(i=0;i<23;i++)
{
for(j=0;j<23;j++)
{Matrix[i][j]=' ';}
}
Matrix[0][22]='>';
Matrix[1][10]='=';
Matrix[2][9]='=';
Matrix[3][9]='>'; Matrix[3][10]='>'; Matrix[3][22]='>';
Matrix[4][9]='>'; Matrix[4][10]='>'; Matrix[4][11]='='; Matrix[4][12]='='; Matrix[4][13]='=';
Matrix[4][14]='='; Matrix[4][22]='>';
Matrix[5][9]='>'; Matrix[5][10]='>'; Matrix[5][11]='>'; Matrix[5][12]='>'; Matrix[5][13]='>';
Matrix[5][14]='>'; Matrix[5][22]='>';
Matrix[6][9]='>'; Matrix[6][10]='>'; Matrix[6][11]='>'; Matrix[6][12]='>'; Matrix[6][13]='>';
Matrix[6][14]='>'; Matrix[6][15]='='; Matrix[6][16]='='; Matrix[6][17]='=';
Matrix[6][18]='='; Matrix[6][19]='='; Matrix[6][20]='='; Matrix[6][21]='='; Matrix[6][22]='>';
Matrix[7][9]='>'; Matrix[7][10]='>'; Matrix[7][11]='>'; Matrix[7][12]='>'; Matrix[7][13]='>';
Matrix[7][14]='>'; Matrix[7][22]='>';
Matrix[8][2]='='; Matrix[8][6]='<';
Matrix[9][1]='>'; Matrix[9][6]='<';
Matrix[10][1]='>'; Matrix[10][6]='<';
Matrix[11][3]='='; Matrix[11][4]='<'; Matrix[11][5]='<'; Matrix[11][6]='<'; Matrix[11][7]='<';
Matrix[12][3]='='; Matrix[12][4]='<'; Matrix[12][5]='<'; Matrix[12][6]='<'; Matrix[12][7]='<';
Matrix[13][5]='='; Matrix[13][6]='<'; Matrix[13][7]='<';
Matrix[14][5]='='; Matrix[14][6]='<'; Matrix[14][7]='<';
Matrix[15][3]='='; Matrix[15][4]='<'; Matrix[15][5]='<'; Matrix[15][6]='<'; Matrix[15][7]='<';
Matrix[16][3]='='; Matrix[16][4]='<'; Matrix[16][5]='<'; Matrix[16][6]='<'; Matrix[16][7]='<';
Matrix[17][3]='='; Matrix[17][4]='<'; Matrix[17][5]='<'; Matrix[17][6]='<'; Matrix[17][7]='<';
Matrix[18][3]='='; Matrix[18][4]='<'; Matrix[18][5]='<'; Matrix[18][6]='<'; Matrix[18][7]='<';
Matrix[19][3]='='; Matrix[19][4]='<'; Matrix[19][5]='<'; Matrix[19][6]='<'; Matrix[19][7]='<';
Matrix[20][3]='='; Matrix[20][4]='<'; Matrix[20][5]='<'; Matrix[20][6]='<'; Matrix[20][7]='<';
Matrix[21][3]='='; Matrix[21][4]='<'; Matrix[21][5]='<'; Matrix[21][6]='<'; Matrix[21][7]='<';
Matrix[22][0]='<'; Matrix[22][3]='<'; Matrix[22][4]='<'; Matrix[22][5]='<'; Matrix[22][6]='<';
Matrix[22][7]='<'; Matrix[22][8]='<'; Matrix[22][22]='=';
for(i=0;i<23;i++)
{
for(j=0;j<23;j++)
{//cout<<Matrix[i][j]<<" ";
}
//cout<<endl;
}
}
char *mark[23]={"S","A","B","E","T","F","i","n","if","then","else","+","-","*","/","<","<=","==","!=",">=",">","=","#"};
int location(Node* p) //在矩阵中找行列
{
int i=0;
char *s,*t;
s=p->data;
if(p->type==1) return 6;
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