词法分析是编译原理的一部分,
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主要分析词的组成的,我是这样认为的,
就比如,你的这个例子,你的词法分析完成后,
可将
-3.14
*
34
+
(
8
-
45
+
3
)
+
9
*
3.4
这些都分别的找到,然后才能运算啊,要不,你知道怎么去运算,
当然,这个,我个人认为,要是做的话,采用栈做比较好,像数据结构那样,一个数字栈,一个符号栈,然后将找到的进行压栈出栈来完成.
我有，这是这学期刚做的，
#include iostream
#include fstream
#include sstream
#include string
#include vector
#include algorithm
using namespace std;
bool isLetter(char ch){
if ((ch='A' ch='Z') || (ch='a' ch='z')) return true;
else return false;
}
bool isDigit(char ch){
if (ch='0' ch='9') return true;
else return false;
}
bool isP(char ch){
if(ch=='+'||ch=='*'||ch=='-'||ch=='/') return true;
//ch==':'||ch==','||ch=='='||ch==';'||ch=='('||ch==')'
else return false;
}
bool isJ(char ch){
if(ch==','||ch==';'||ch=='.'||ch=='('||ch==')'||ch=='['||ch==']'||ch=='='||ch==':'||ch==''||ch==''||ch=='{'||ch=='}'||ch=='#') return true;
//
else return false;
}
bool isBlank(char ch){
if(ch==' '||ch=='\t') return true;
else return false;
}
int main(){
string src,ste,s;
char ch0,ch,ch1[2];
char ktt[48][20]={"and","begin","const","div","do","else","end","function","if","integer",
"not","or","procedure","program","read","real","then","type","var","while","write","标识符","无符号数",
",",";",":",".","(",")","[","]","..","++","--","+","-","*","/","=","","","","="
,"=",":=","{","}","#"};
int pos=0;
FILE *fp;
fp=fopen("d:\\in.txt","r");
ch0=fgetc(fp);
while(ch0!=EOF)
{
//if(ch0!='\t'){src+=ch0;}
src+=ch0;
ch0=fgetc(fp);
}
src+='#';
coutsrcendl;
ch=src[pos++];
ste=" ";
for(int j=0;j47;j++){coutjktt[j]endl;}
cout"词法分析:\n";
while(ch!='#')
{
char str[20];
if(ch!='\n')
{
if(isDigit(ch))
{ //判断常数
int i=0;
while(isDigit(ch)||ch=='.')
{
str[i++]=ch;
//i++;
ch=src[pos++];
}
str[i]='\0';
ste=ste+"|"+"22";
coutstr;
continue;
}
else if(isLetter(ch))
{ //判断字符
int i=0,j;
while(isLetter(ch)||isDigit(ch))
{
str[i++]=ch;
//i++;
ch=src[pos++];
}
str[i]='\0';
for(j=0;j21;j++){ //判断是否关键字
int t=strcmp(str,ktt[j]);
if(t==0) {
stringstream ss;
ste+="|";
ssste;ssj;
ssste;
break;
}
}
if(j==21){ste=ste+"|"+"21";}
// cout" ";
coutstr;
continue;
}
else if(isP(ch)){ ///判断是否运算符
int i=0,j;
str[i++]=ch;
str[i]='\0';
for(j=34;j38;j++){
int t=strcmp(str,ktt[j]);
if(t==0) {
stringstream ss;
ste+="|";
ssste;ssj;
ssste;
break;
}
}
coutstr;
ch=src[pos++];
continue;
}
else if(isJ(ch)) //判断是否界符
{
int i=0,j;
while(isJ(ch))
{
str[i++]=ch;
ch=src[pos++];
}
str[i]='\0';
for(j=23;j47;j++){
int t=strcmp(str,ktt[j]);
if(t==0) {
stringstream ss;
ste+="|";
ssste;ssj;
ssste;
break;
}
}
coutstr;
continue;
}
else if(isBlank(ch))
{
coutch;
ch=src[pos++];
continue;
}
}
else{
coutsteendl;
ste=" ";
}
ch=src[pos++];
}
return 0;
}
还有运行效果图，和实验报告 ，你要的话留下邮箱
#includestdio.h #includestring.h #define nmax 14 #define norw 8 /*关键字个数*/ #define al 10 #define getchdo if(-1==getch()) return -1 #define getsymdo if(-1==getsym()) return -1 char ch; /*获取字符的缓冲区,getch使用*/ char word[norw][al]; /*保留字*/ char fname[al]; /*文件名*/ char id[al+1]; /*存放标识符或保留字*/ char line[81]; /*读取行缓冲区*/ char a[al+1]; /*临时符号,多处的字节用于存放0*/ char anum[nmax+1]; /*临时符号,存放number*/ char inum[nmax+1]; /*存放常数*/ int cc,ll; /*cc表示当前字符(ch)的位置*/ int num; /*常数*/ int err; //错误计数器 FILE * fin; FILE * fout; FILE * fas; /*词法分析结果文件*/ /*函数执行出错,退出程序*/ int getch(); /*读取一行字符*/ int getsym(); /*从文件fin中读取一行字符,保存到字符缓冲区line中*/ int getch() { if(cc==ll) { ll=0; cc=0; ch=' '; while(ch!=10) { if(feof(fin)) { return -1; } if(EOF==fscanf(fin,"%c",ch)) { line[ll]=0; break; } line[ll]=ch; ll++; } } ch=line[cc]; cc++; return 0; } /*读取一个分词*/ int getsym() { int i,j,k; while(ch==' '||ch==10||ch==9) //忽略空格,换行和TAB { getchdo; } if(ch='a'ch='z') //判断是否为关键字或标识符 { k=0; do{ if(kal){ a[k]=ch; k++; } getchdo; }while(ch='a'ch='z'||ch='0'ch='9'); a[k]=0; if(kal)printf("error"); strcpy(id,a); i=0; j=norw-1; do{ k=(i+j)/2; if(strcmp(id,word[k])=0) {j=k-1; } if(strcmp(id,word[k])=0) { i=k+1; } }while(i=j); if(i-1j) { fprintf(fas,"Keyword %s\n",id);/*分词为关键字*/ } return 0; } 这里面的代码写不开，你加我的QQ：412686686，我直接传文件给你好了，你这个问题的代码太多了，我刚好昨天给别人写了一个。
//给你课程设计的词法部分呵呵
#include iostream
#include fstream
#include stack
#include map
#include string
using namespace std;
#define zhengshu 1 //int
#define IF 2 //if
#define ELSE 3 //else
#define shishu 4 //float
#define PRINT 5 //print
#define ID 6 //identify
#define CONSTANT 7 //constant
#define op_fuzhi 8 //=
#define op_add 9 //+
#define op_mul 10 //*
#define op_2star 11 //**
#define div_fenhao 12 //;
#define syl_ls 13 //(
#define syl_rs 14 //)
#define syl_lb 15 //{
#define syl_rb 16 //}
#define sbl_lm 17 //[
#define sbl_rm 18 //]
#define op_sub 19 //-
#define op_div 20 // /
#define div_douhao 21 //,
#define rop_yu 22 //
#define op_or 23 //||
#define rop_fei 24 //!
#define rop_equal 25 //==
#define rop_dayu 26 //
#define rop_xiaoyu 27 //
#define rop_buxiaoyu 28 //=
#define rop_budayu 29 //=
#define rop_uneql 30 //!=
#define TEMP 31
#define NULL 0
#define JMP 32
#define GOTO 33 //goto标识
/*****************************重要数据结构的声明开始*************************/
struct delos
{
int code,value;
}*result; //结果
//变量表
struct analyse
{
int state;
char sign;
};
struct list
{
int value;
list *next;
};
//条件语句的LR(1)分析表,110表示接受，999表示出错
int table[38][20]={
/*0*/{3,999,999,999,999,999,999,999,999,999,999,999,4,999,1,2,999,999,999,999},
/*1*/{999,999,999,999,999,999,999,999,999,999,999,999,999,110,999,999,999,999,999,999},
/*2*/{74,999,999,999,999,999,999,999,999,999,999,999,74,74,999,999,999,999,5,999},
/*3*/{999,6,999,999,999,999,999,999,999,999,999,999,999,999,999,999,999,999,999,999},
/*4*/{999,999,999,999,7,999,999,999,999,999,999,999,999,999,999,999,999,999,999,999},
/*5*/{999,999,999,999,999,999,999,999,999,999,999,999,999,61,999,999,999,999,999,999},
/*6*/{999,12,999,999,999,999,999,9,999,999,999,11,13,999,999,999,8,10,999,999},
/*7*/{999,12,999,999,999,999,999,999,999,999,999,11,13,999,999,999,999,14,999,999},
/*8*/{999,999,15,999,999,16,17,999,999,999,999,999,999,999,999,999,999,999,999,999},
/*9*/{999,12,999,999,999,999,999,9,999,999,999,11,13,999,999,999,18,10,999,999},
/*10*/{999,999,999,999,999,999,999,999,19,20,21,999,999,999,999,999,999,999,999,999},
/*11*/{999,12,999,999,999,999,999,999,999,999,999,11,13,999,999,999,999,22,999,999},
/*12*/{999,12,999,999,999,999,999,999,999,999,999,11,13,999,999,999,999,23,999,999},
/*13*/{999,999,73,73,999,73,73,999,73,73,73,999,999,73,999,999,999,999,999,999},
/*14*/{999,999,999,64,999,999,999,999,999,20,21,999,999,64,999,999,999,999,999,999},
/*15*/{74,999,999,999,999,999,999,999,999,999,999,999,74,74,999,999,999,999,24,999},
/*16*/{74,999,999,999,999,999,999,999,999,999,999,999,74,74,999,999,999,999,999,25},
/*17*/{74,999,999,999,999,999,999,999,999,999,999,999,74,74,999,999,999,999,999,26},
/*18*/{999,999,67,999,999,67,67,999,999,999,999,999,999,999,999,999,999,999,999,999},
/*19*/{999,12,999,999,999,999,999,999,999,999,999,11,13,999,999,999,999,27,999,999},
/*20*/{999,12,999,999,999,999,999,999,999,999,999,11,13,999,999,999,999,28,999,999},
/*21*/{999,12,999,999,999,999,999,999,999,999,999,11,13,999,999,999,999,29,999,999},
/*22*/{999,999,71,71,999,71,71,999,71,71,71,999,999,71,999,999,999,999,999,999},
/*23*/{999,999,30,999,999,999,999,999,999,20,21,999,999,999,999,999,999,999,999,999},
/*24*/{3,999,999,999,999,999,999,999,999,999,999,999,4,999,999,31,999,999,999,999},
/*25*/{999,12,999,999,999,999,999,9,999,999,999,11,13,999,999,999,32,10,999,999},
/*26*/{999,12,999,999,999,999,999,9,999,999,999,11,13,999,999,999,33,10,999,999},
/*27*/{999,999,68,999,999,68,68,999,999,20,21,999,999,999,999,999,999,999,999,999},
/*28*/{999,999,69,69,999,69,69,999,69,69,21,999,999,69,999,999,999,999,999,999},
/*29*/{999,999,70,70,999,70,70,999,70,70,70,999,999,70,999,999,999,999,999,999},
/*30*/{999,999,72,72,999,72,72,999,72,72,72,999,999,72,999,999,999,999,999,999},
/*31*/{999,999,999,75,999,999,999,999,999,999,999,999,999,63,999,999,999,999,999,34},
/*32*/{999,999,65,999,999,65,65,999,999,999,999,999,999,999,999,999,999,999,999,999},
/*33*/{999,999,66,999,999,16,66,999,999,999,999,999,999,999,999,999,999,999,999,999},
/*34*/{999,999,999,35,999,999,999,999,999,999,999,999,999,999,999,999,999,999,999,999},
/*35*/{74,999,999,999,999,999,999,999,999,999,999,999,74,74,999,999,999,999,36,999},
/*36*/{3,999,999,999,999,999,999,999,999,999,999,999,4,999,999,37,999,999,999,999},
/*37*/{999,999,999,62,999,999,999,999,999,999,999,999,999,62,999,999,999,999,999,999}
};
/*****************************重要数据结构的声明结束*************************/
/*********************************全局变量声明开始**************************/
int place=1;
int nextpos=1;
stacklist * stknext;
stacklist * stktrue;
stacklist * stkfalse;
stackint stkpos;
stackdelos stktemp;//常量，变量，临时变量
delos temp;
delos gen[50][4];//生成的三地址
string str[31]={"","int","if","else","float","print","标识符","常数",
"=","+","*","**",";","(",")",
"{","}","[","]","-","/",",","","||","!",
"==","","","=","=","!="};
//变量
string *var;
int varlen=0,nowvar=1;
//常量
float *myconst;
int constlen=0,nowconst=1;
int resultlen=0,nowresult=0;
/*********************************全局变量声明结束**************************/
void renewresult()
{
delos *p3=result;
int i;
resultlen+=10;
result=new delos[resultlen];
for(i=0;iresultlen;i++)
{ result[i].code=p3[i].code;
result[i].value=p3[i].value;
}
delete[] p3;
}
void renewvar()
{
string *p1=var;
int i;
varlen+=10;
var=new string[varlen];
for(i=0;inowvar;i++)
var[i]=p1[i];
delete[] p1;
}
void renewconst()
{
float *p2=myconst;
int i;
constlen+=10;
myconst=new float[constlen];
for(i=0;inowconst;i++)
myconst[i]=p2[i];
delete[] p2;
}
bool isletter(char c) //判别是否字母
{
if(c64c91||c96c123)
return true;
return false;
}
bool isdigital(char c) //判别是否数字
{ if(c47c58)
return true;
return false;
}
int reserve(char c[],int i)
{
string s(c,0,i);
for(int j=1;j7;j++)
if(s==str[j])
return j;
return 0;
}
void insertresult(int code,int value)
{ if(nowresultresultlen)
renewresult();
result[nowresult].code=code;
result[nowresult++].value=value;
}
void insertid(char c[],int i)
{ string s(c,0,i);
insertresult(ID,nowvar);
if(nowvarvarlen)
renewvar();
var[nowvar++]=s;
}
//插入常数，为浮点型
void insertconst(char c[],int i)
{ int d=0,j;
float a=0,b=1;
while(c[d]!='.'di)
d++;
for(j=d-1;j=0;j--)
{ a=a+(c[j]-48)*b;
b=b*10;
}
b=10;
for(j=d+1;ji;j++)
{a=a+(c[j]-48)/b;
b=b*10;
}
insertresult(CONSTANT,nowconst);
if(nowconstconstlen)
renewconst();
myconst[nowconst++]=a;
}
/**********************************词法分析函数开始***********************/
void wordanalyse()
{
char strtoken[10];
int i=0,code;
char ch;
ifstream myfile;
myfile.open("sourcefile.txt");
if(!myfile)
{ cout"Can not open input file !"endl;
return;
}
while(!myfile.eof())
{ i=0;
for(ch=myfile.get();ch==' '||ch==13||ch==10;ch=myfile.get())
;
if(isletter(ch))
{while(isletter(ch)||isdigital(ch))
{strtoken[i++]=ch;
ch=myfile.get();
}
myfile.seekg(-1,ios::cur);
code=reserve(strtoken,i);
if(code==0)
insertid(strtoken,i);
else
{insertresult(code,0);
}
}
else if(isdigital(ch))
{while(isdigital(ch)||ch=='.')
{strtoken[i++]=ch;
ch=myfile.get();
}
myfile.seekg(-1,ios::cur);
insertconst(strtoken,i);
}
else if(ch=='=')
{ ch=myfile.get();
if(ch=='=')
insertresult(rop_equal,0);
else
{insertresult(op_fuzhi,0);
myfile.seekg(-1,ios::cur);
}
}
else if(ch=='+')
{insertresult(op_add,0);
}
else if(ch=='*')
{ ch=myfile.get();
if(ch=='*')
insertresult(op_2star,0);
else
{insertresult(op_mul,0);
myfile.seekg(-1,ios::cur);
}
}
else if(ch==';')
{ insertresult(div_fenhao,0);
}
else if(ch=='(')
{insertresult(syl_ls,0);
}
else if(ch==')')
{insertresult(syl_rs,0);
}
else if(ch=='{')
{ insertresult(syl_lb,0);
}
else if(ch=='}')
{ insertresult(syl_rb,0);
}
else if(ch=='[')
{ insertresult(sbl_lm,0);
}
else if(ch==']')
{ insertresult(sbl_rm,0);
}
else if(ch=='-')
{ insertresult(op_sub,0);
}
else if(ch=='/')
{ insertresult(op_div,0);
}
else if(ch==',')
{ insertresult(div_douhao,0);
}
else if(ch=='')
{ ch=myfile.get();
if(ch=='')
insertresult(rop_yu,0);
else
{
myfile.seekg(-1,ios::cur);
myfile.get(strtoken,10);
cout"ERROR :"strtokenendl;
}
}
else if(ch=='|')
{ ch=myfile.get();
if(ch=='|')
insertresult(op_or,0);
else
{
myfile.seekg(-1,ios::cur);
myfile.get(strtoken,10);
cout"ERROR :"strtokenendl;
}
}
else if(ch=='!')
{ ch=myfile.get();
if(ch=='=')
insertresult(rop_uneql,0);
else
{insertresult(rop_fei,0);
myfile.seekg(-1,ios::cur);
}
}
else if(ch=='')
{ ch=myfile.get();
if(ch=='=')
insertresult(rop_buxiaoyu,0);
else
{insertresult(rop_dayu,0);
myfile.seekg(-1,ios::cur);
}
}
else if(ch=='')
{ ch=myfile.get();
if(ch=='=')
insertresult(rop_budayu,0);
else
{insertresult(rop_xiaoyu,0);
myfile.seekg(-1,ios::cur);
}
}
else
{if(ch!=-1)
{myfile.seekg(-1,ios::cur);
myfile.get(strtoken,10);
cout"ERROR :"strtokenendl;
myfile.seekg(1,ios::cur);
}
}
}
myfile.close();
cout"词法分析成功啦!!"endl;
}
/**********************************词法分析函数结束***********************/
#include "stdio.h" /*定义I/O库所用的某些宏和变量*/
#include "string.h" /*定义字符串库函数*/
#include "conio.h" /*提供有关屏幕窗口操作函数*/
#include "ctype.h" /*分类函数*/
char prog[80]={'\0'},
token[8]; /*存放构成单词符号的字符串*/
char ch;
int syn, /*存放单词字符的种别码*/
n,
sum, /*存放整数型单词*/
m,p; /*p是缓冲区prog的指针，m是token的指针*/
char *rwtab[6]={"begin","if","then","while","do","end"};
void scaner(){
m=0;
sum=0;
for(n=0;n8;n++)
token[n]='\0';
ch=prog[p++];
while(ch==' ')
ch=prog[p++];
if(isalpha(ch)) /*ch为字母字符*/{
while(isalpha(ch)||isdigit(ch)) /*ch 为字母字符或者数字字符*/{
token[m++]=ch;
ch=prog[p++];}
token[m++]='\0';
ch=prog[p--];
syn=10;
for(n=0;n6;n++)
if(strcmp(token,rwtab[n])==0) /*字符串的比较*/{
syn=n+1;
break;}}
else
if(isdigit(ch)) /*ch是数字字符*/{
while(isdigit(ch)) /*ch是数字字符*/{
sum=sum*10+ch-'0';
ch=prog[p++];}
ch=prog[p--];
syn=11;}
else
switch(ch){
case'':m=0;token[m++]=ch;ch=prog[p++];
if(ch==''){
syn=21;
token[m++]=ch;}
else if(ch=='='){
syn=22;
token[m++]=ch;}
else{
syn=20;
ch=prog[p--];}
break;
case'':m=0;token[m++]=ch;ch=prog[p++];
if(ch=='='){
syn=24;
token[m++]=ch;}
else{
syn=23;
ch=prog[p--];}
break;
case':':m=0;token[m++]=ch;ch=prog[p++];
if(ch=='='){
syn=18;
token[m++]=ch;}
else{
syn=17;
ch=prog[p--];}
break;
case'+':syn=13;token[0]=ch;break;
case'-':syn=14;token[0]=ch;break;
case'*':syn=15;token[0]=ch;break;
case'/':syn=16;token[0]=ch;break;
case'=':syn=25;token[0]=ch;break;
case';':syn=26;token[0]=ch;break;
case'(':syn=27;token[0]=ch;break;
case')':syn=28;token[0]=ch;break;
case'#':syn=0;token[0]=ch;break;
default:syn=-1;}}
main()
{
printf("\n\nThe significance of the figures:\n"
"1.figures 1 to 6 said Keyword\n"
"2.figures 10 and 11 said Other indicators\n"
"3.figures 13 to 28 said Operators\n");
p=0;
printf("\nplease input string:\n");
do {
ch=getchar();
prog[p++]=ch;
}while(ch!='#');
p=0;
do{
scaner();
switch(syn){
case 11: printf("(%d,%d)\n",syn,sum);break;
case -1: printf("\n ERROR;\n");break;
default: printf("(%d,%s)\n",syn,token);
}
}while(syn!=0);
getch();
}
程序测试结果
对源程序begin x:=9: if x9 then x:=2*x+1/3; end #的源文件，经过词法分析后输出如下图5-1所示：
具体的你在修改修改吧
