实验要求：
1、对源程序进行理解，从PL0文档中抽取出词法部分的代码，单独作为一个程序，变成一个词法程序，用visual6.0或者Dev c++进行编译，编译成为可执行文件；
2、对输出的文件进行检验，用PL0验证源程序作为词法验证输入源程序，对其进行读入
3、单词序列二元组结果的显示并保存成结构文件；
4、指出抽取的PL0词法分析程序中的标识符、关键字、界符、运算符，常数有哪些；
5、画出状态转移图。
PL0验证源程序文件.txt
词法分析器源程序.cpp
#include<stdio.h>
#include<string.h>
#include<stdlib.h>
void init();
void getsym();
/* 符号 */
enum symbol
{
nul,ident,number,plus,minus,times,slash,oddsym,eql,neq,
lss,leq,gtr,geq,lparen,rparen,comma,semicolon,period,becomes,
beginsym,endsym,ifsym,thensym,whilesym,writesym,readsym,dosym,callsym,
constsym,varsym,procsym,programsym,
};
#define norw 14 /*关键字个数*/
#define al 10 //符号的最大的长度
#define nmax 10 //number的最大位数
char word [norw][al]; //保留字13个
char ch; /* 获取字符的缓冲区 */
enum symbol sym; /* 当前的符号 */
enum symbol wsym[norw]; /* 保留字对应的符号值 */
enum symbol ssym[256]; //单字符的符号值
FILE *fin,*fout;
int main()
{
printf("请输入结果要保存的文件:\n"); //词法分析之后的结果要输出到的文件
char outname[30],inname[30];
scanf("%s",outname);
if((fout=fopen(outname,"w"))==NULL)
{
printf("不能打开文件!");
exit(0);
}
printf("请输入需要词法分析的源程序:\n"); //需要词法分析的源程序
scanf("%s",inname);
if((fin=fopen(inname,"r"))==NULL)
{
printf("不能打开文件!\n");
exit(0);
}
ch=fgetc(fin);
while(ch!=EOF) //EOF实际是-1，用来表示文本文件的结束
{
getsym();
}
}
//读取源文件
void getsym()
{
long m;
char id[al+1],a[al+1];
int i,k;
init();
if(ch==' '||ch==10||ch==9) /*忽略空格、换行和TAP*/
{
ch=fgetc(fin);
}
else
{
if(ch>='a'&&ch<='z'||ch>='A'&&ch<='Z') /*名字或保留字以a..z开头*/
{
k=0;
do /*搜索当前符号是否为保留字*/
{
if(k<al)
{
a[k]=ch;
k++;
}
ch=fgetc(fin);
}while ((ch>='a'&&ch<='z'||ch>='0'&&ch<='9')||(ch>='A'&&ch<='Z'||ch>='0'&&ch<='9'));
a[k]=0;
strcpy(id,a);
//将识别出来的字符和已定义的标示符作比较， 判断是否是关键字
for(i=0;i<norw;i++)
{
if(strcmp(id,word[i])==0)
{
sym=wsym[i];
printf("%s %ssym\n",id,id);
fprintf(fout,"%s %ssym\n",id,id);
break;
}
else
{
if(i==(norw-1))
{
sym=ident;
printf("%s ident\n",id);
fprintf(fout,"%s ident\n",id);
}
}
}
}
else
{
if(ch>='0'&&ch<='9') /*检测是否为数字：以0..9开头*/
{
k=0;
m=0;
sym=number;
do
{
m=10*m+ch-'0';
k++;
ch=getc(fin);
}while(ch>='0'&&ch<='9'); /*获取数字的值*/
if(k>=nmax)
{
printf(" error!数值太大！ \n");
//exit(0);
}
printf("%d number\n",m);
fprintf(fout,"%d number\n",m);
}
else
{
if(ch==':') /*检测赋值符号*/
{
ch=getc(fin);
if(ch=='=')
{
sym=becomes;
printf(":= becomes\n");
fprintf(fout,":= becomes\n");
ch=fgetc(fin);
}
else
{
sym=nul;
printf(": nul\n"); /*不能识别的符号*/
fprintf(fout,": nul\n");
}
}
else
{
if(ch=='<') /*检测小于或小于等于符号*/
{
ch=fgetc(fin);
if(ch=='=')
{
sym=leq;
printf("<= lep\n");
fprintf(fout,"<= lep\n");
ch=fgetc(fin);
}
else
{
sym=lss;
printf("< lss\n");
fprintf(fout,"< lss\n");
}
}
else
{
if(ch=='>') /*检测大于或大于等于符号*/
{
ch=fgetc(fin);
if(ch=='=')
{
sym=geq;
printf(">= geq\n");
fprintf(fout,">= geq\n");
ch=fgetc(fin);
}
else
{
sym=gtr;
printf("> gtr\n");
fprintf(fout,"> gtr\n");
}
}
else /*当符号不满足上述条件时，全部按照单字符符号处理*/
{
sym=ssym[ch];
if(ch=='+'){printf("+ plus\n");fprintf(fout,"+ plus\n");ch=fgetc(fin);}
else
if(ch=='-'){printf("- minus\n");fprintf(fout,"- minus\n");ch=fgetc(fin);}
else
if(ch=='*'){printf("* times\n");fprintf(fout,"* times\n");ch=fgetc(fin);}
else
if(ch=='/'){printf("/ slash\n");fprintf(fout,"/ slash\n");ch=fgetc(fin);}
else
if(ch=='('){printf("( lparen\n");fprintf(fout,"( lparen\n");ch=fgetc(fin);}
else
if(ch==')'){printf(") rparen\n");fprintf(fout,") rparen\n");ch=fgetc(fin);}
else
if(ch=='='){printf("= eql\n");fprintf(fout,"= eql\n");ch=fgetc(fin);}
else
if(ch==','){printf(", comma\n");fprintf(fout,", comma\n");ch=fgetc(fin);}
else
if(ch=='#'){printf("# neq\n");fprintf(fout,"# neq\n");ch=fgetc(fin);}
else
if(ch=='.'){printf(". period\n");fprintf(fout,". period\n");ch=fgetc(fin);}
else
if(ch==';'){printf("; semicoln\n");fprintf(fout,"; semicoln\n");ch=fgetc(fin);}
else{printf("%c nul\n",ch);fprintf(fout,"%c nul\n",ch);ch=fgetc(fin);}
}
}
}
}
}
}
}
//对关键字等实现初始化
void init()
{
/*设置单字符符号*/
int i;
for(i=0;i<=255;i++)
{
ssym[i]=nul;
}
ssym['+']=plus;
ssym['-']=minus;
ssym['*']=times;
ssym['/']=slash;
ssym['(']=lparen;
ssym[')']=rparen;
ssym['=']=eql;
ssym[',']=comma;
ssym['.']=period;
ssym['#']=neq;
ssym[';']=semicolon;
/*设置保留字名字，按照字母表顺序，便于折半查找*/
strcpy(&(word[0][0]),"begin");
strcpy(&(word[1][0]),"call");
strcpy(&(word[2][0]),"const");
strcpy(&(word[3][0]),"do");
strcpy(&(word[4][0]),"end");
strcpy(&(word[5][0]),"if");
strcpy(&(word[6][0]),"odd");
strcpy(&(word[7][0]),"procedure");
strcpy(&(word[8][0]),"read");
strcpy(&(word[9][0]),"program");
strcpy(&(word[10][0]),"var");
strcpy(&(word[11][0]),"whlie");
strcpy(&(word[12][0]),"write");
strcpy(&(word[13][0]),"then");
/*设置保留字符号*/
wsym[0]=beginsym;
wsym[1]=callsym;
wsym[2]=constsym;
wsym[3]=dosym;
wsym[4]=endsym;
wsym[5]=ifsym;
wsym[6]=oddsym;
wsym[7]=procsym;
wsym[8]=readsym;
wsym[9]=programsym;
wsym[10]=varsym;
wsym[11]=whilesym;
wsym[12]=writesym;
wsym[13]=thensym;
}
输入要保存的二元组文件名字和要词法分析的源程序文件
然后运行该程序
该目录下已经生成了test.txt 二元组文件
生成的test.txt 二元组文件
指出抽取的PL0词法分析程序中的标识符、关键字、界符、运算符，常数有哪些；
标识符:字母数字串
关键字:begin end if then else while write read do call Constantine
var procedure repeat until
界符: , . ; ( )
运算符: + - * / := = <>(#) < <= > >=
常数:整数
5、画出状态转移图。
实验完成