词法分析器的设计与实现.docx
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词法分析器的设计与实现.docx
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词法分析器的设计与实现
词法分析器的设计与实现
《编译原理》课程实验报告
实验题目:
某种简单程序语言的词法分析器的设计与实现
专业:
计算机科学与技术
班级:
11060341
学号:
11060341
姓名:
实验目的:
设计一个词法分析程序,理解词法分析器实现的原理,掌握程序设计语言中的各类单词的词法分析方法,加深对词法分析原理的理解。
实验任务:
词法分析是从左向右扫描每行源程序的符号,拼成单词,换成统一的二元式(单词种别,单词符号的属性值)表示。
对给定的程序经过词法分析器识别一个个单词符号,并以二元式
(单词种别,单词符号的属性值)显示,本程序则是经过对给定程序段分析后以单词符号和文字提示显示)
实验流程:
程序清单:
#include
#include
#include
usingnamespacestd;
intk=0;
structword
{
charname[10];
intkind;
}word[1000];
charkey[35][10]={"scanf","short","int","long","float","double","char","struct","union",
"printf","typedef","const","unsigned","signed","extern","register","static",
"volatile","void","if","else","switch","case","for","do","while","goto",
"continue","break","default","sizeof","return","include","bool"
};
boolcmp(chara[])
{
inti;
for(intk=0;k<35;k++)
{
if(strcmp(a,key[k])==0)
return1;
}
return0;
}
intmain()
{
#ifdefLOCAL
freopen("in.txt","r",stdin);
freopen("out.txt","w",stdout);
#endif
intp,q,flag;
chara[1000],b[10],ch;
while(gets(a))
{
p=0;
intlen=strlen(a);
while(p { ch=a[p]; memset(b,0,sizeof(b)); while(ch=='') { p++; ch=a[p]; } if((ch>='a'&&ch<='z')||(ch>='A'&&ch<='Z')||ch=='_') { flag=0; q=0; while((ch>='a'&&ch<='z')||(ch>='A'&&ch<='Z')||ch=='_'||(ch>='0'&&ch<='9')) { if((ch>='0'&&ch<='9')||ch=='_') flag=1; b[q++]=ch; p++; ch=a[p]; } if(flag==1) { strcpy(word[k].name,b); word[k++].kind=1; } elseif(flag==0) { if(ch=='\''||ch=='"') { strcpy(word[k].name,b); word[k++].kind=2; } elseif(cmp(b)==1) { strcpy(word[k].name,b); word[k++].kind=3; } else { strcpy(word[k].name,b); word[k++].kind=1; } } } elseif((ch>='0'&&ch<='9')||ch=='-') { intt=p-1; if(a[t]>='0'&&a[t]<='9'||a[t]>='a'&&a[t]<='z'||a[t]>='A'&&a[t]<='Z') { p++; ch=a[p]; if(ch=='-'||ch=='=') { b[0]='-'; b[1]=ch; strcpy(word[k].name,b); word[k++].kind=5; ch=a[++p]; } else { b[0]='-'; strcpy(word[k].name,b); word[k++].kind=5; } } else { q=0; b[q++]=ch; p++; ch=a[p]; while((ch>='0'&&ch<='9')||ch=='.') { b[q++]=ch; p++; ch=a[p]; } strcpy(word[k].name,b); word[k++].kind=2; } } elseif(ch=='('||ch==')'||ch=='['||ch==']'||ch=='{'||ch=='}'||ch==','||ch==';'||ch==': '||ch=='\''||ch=='"')//ch=='('||ch==')'||ch=='['||ch==']'||ch=='{'||ch=='}'|| { b[0]=ch; strcpy(word[k].name,b); word[k++].kind=4; ch=a[++p]; } elseif(ch=='%'||ch=='^') { b[0]=ch; strcpy(word[k].name,b); word[k++].kind=5; ch=a[++p]; } elseif(ch=='+') { p++; ch=a[p]; if(ch=='+'||ch=='=') { b[0]='+'; b[1]=ch; strcpy(word[k].name,b); word[k++].kind=5; ch=a[++p]; } else { b[0]='+'; strcpy(word[k].name,b); word[k++].kind=5; } } elseif(ch=='*') { p++; ch=a[p]; if(ch=='*'||ch=='=') { b[0]='*'; b[1]=ch; strcpy(word[k].name,b); word[k++].kind=5; ch=a[++p]; } else { b[0]='*'; strcpy(word[k].name,b); word[k++].kind=5; } } elseif(ch=='/') { p++; ch=a[p]; if(ch=='/'||ch=='=') { b[0]='/'; b[1]=ch; strcpy(word[k].name,b); word[k++].kind=5; ch=a[++p]; } else { b[0]='/'; strcpy(word[k].name,b); word[k++].kind=5; } } elseif(ch=='=') { p++; ch=a[p]; if(ch=='=') { b[0]=b[1]='='; strcpy(word[k].name,b); word[k++].kind=5; ch=a[++p]; } else { b[0]='='; strcpy(word[k].name,b); word[k++].kind=5; } } elseif(ch=='>') { p++; ch=a[p]; if(ch=='>'||ch=='=') { b[0]='>'; b[1]=ch; strcpy(word[k].name,b); word[k++].kind=5; ch=a[++p]; } else { b[0]='>'; strcpy(word[k].name,b); word[k++].kind=5; } } elseif(ch=='<') { p++; ch=a[p]; if(ch=='<'||ch=='=') { b[0]='<'; b[1]=ch; strcpy(word[k].name,b); word[k++].kind=5; ch=a[++p]; } else { b[0]='<'; strcpy(word[k].name,b); word[k++].kind=5; } } elseif(ch=='! ') { p++; ch=a[p]; if(ch=='=') { b[0]='! '; b[1]='='; strcpy(word[k].name,b); word[k++].kind=5; ch=a[++p]; } else { b[0]='! '; strcpy(word[k].name,b); word[k++].kind=5; } } elseif(ch=='&') { p++; ch=a[p]; if(ch=='&') { b[0]=b[1]='&'; strcpy(word[k].name,b); word[k++].kind=5; ch=a[++p]; } else { b[0]='&'; strcpy(word[k].name,b); word[k++].kind=5; } } elseif(ch=='|') { p++; ch=a[p]; if(ch=='|') { b[0]=b[1]='|'; strcpy(word[k].name,b); word[k++].kind=5; ch=a[++p]; } else { b[0]='|'; strcpy(word[k].name,b); word[k++].kind=5; } } } } for(inti=0;i { switch(word[i].kind) { case1: { printf("(标识符,"); break; } case2: { printf("(常量,"); break; } case3: { printf("(关键字,"); break; } case4: { printf("(界符,"); break; } case5: { printf("(运算符,"); break; } } printf("%s)\n",word[i].name); } inta1=0,a2=0,a3=0,a4=0,a5=0; for(inti=0;i { if(word[i].kind==1) a1++; elseif(word[i].kind==2) a2++; elseif(word[i].kind==3) a3++; elseif(word[i].kind==4) a4++; elseif(word[i].kind==5) a5++; } printf("标识符: %d\n常量: %d\n关键字: %d\n界符: %d\n运算符: %d\n",a1,a2,a3,a4,a5); return0; } 运行结果:
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