DOC《编译原理实验报告》

编译原理实验报告 实验目的 通过本次实验,掌握词法分析、语法分析和产生四元式的设计.

实验内容 词法分析 词法分析是编制一个读单词的过程,从输入的源程序中,识别出各个具有独立意义的单词,即基本保留字、标识符、常数、运算符、分隔符五大类.并依次输出各个单词的内部编码及单词符号自身值.程序语言的单词符号一般分为五种:关键字:有if、while等;

标识符:常量名、变量名…;

常数;

运算符:+、-、*等;

界限符:等. 词法分析的功能是输入源程序,输出单词符号.词法分析器的单词符号常常表示成以下的二元式(单词,单词种类). 在本实验中,以分析如下代码: main( ) { int a, b, c ;

a =

3 ;

b =

2 ;

c = (a+b)*5+3 ;

} 要求实验输出的结果是每一个单词对应于一个单词种类,使用一个二元式表示的. 其主要代码: void Scan() { struct stat buffer;

int i = 0;

char ch;

char filename[40];

FILE *inFile;

printf( Please input the file name: );

gets(filename);

stat( filename , &

buffer);

file = (char*)malloc(sizeof(buffer.st_size));

if((inFile=fopen( source.txt , r ))==NULL) { printf( Cannot open file. );

getchar();

exit(0);

} while((ch = getc(inFile)) != EOF) file[i++] = ch;

fclose(inFile) ;

file[i++] = '

\0'

;

fileLength = i;

initRecord();

printf( \n-词法分析-n );

while((ch = getCharacter(0'

) { if((ch != '

\n'

) &

&

(ch ch != '

\t'

)) { if( islower(ch) || isupper(ch) || ch == '

_'

) recogId(ch);

else if(isdigit(ch)) recogDigit(ch);

else recogOther(ch);

};

} insertToken(13,-1);

} void recogId(char ch) { int i = 0;

int code;

int keyword = 0;

strcpy(strToken, );

while(islower(ch) || isupper(ch) || isdigit(ch)) { strToken[i] = ch;

ch = getCharacter();

i++;

} strToken[i] = '

\0'

;

cursor--;

row--;

code = Reserve();

if (code) printf( %s\t关键字\n ,strToken);

else printf( %s\t标识符\n ,strToken);

for(i = 0;

i <

13;

i++) { if(strcmp(record[i].symbol,strToken) == 0) { insertToken(record[i].id, -1);

keyword = 1;

} } if(!keyword) { struct entryType *head, * tempEntry;

int word = 0;

if(headEntry == NULL) { head = (struct entryType*)malloc(sizeof(struct entryType));

strcpy(head->

idName, strToken);

head->

address = entry;

head->

type = NULL;

head->

next = NULL;

headEntry = tailEntry = head;

entry++;

insertToken(3, entry - 1);

} else { tempEntry = headEntry;

while(tempEntry != NULL) { if(strcmp(tempEntry->

idName, strToken) == 0) { insertToken(3, tempEntry->

address);

word = 1;

} tempEntry = tempEntry->

next;

} if(!word) { head = (struct entryType*)malloc(sizeof(struct entryType));

strcpy(head->

idName, strToken);

head->

address = entry;

head->

type = NULL;

head->

next = NULL;

tailEntry = tailEntry->

next = head;

entry++;

insertToken(3, entry - 1);

} } } } //识别数字 void recogDigit(char ch) { int i = 0;

do { i = i *

10 + ch - '

0'

;

ch = getCharacter();

}while(isdigit(ch));

row--;

cursor--;

printf( %d\t常数\n ,i);

insertDigit(i);

insertToken(2, digit - 1);

} //识别界限符、运算符 void recogOther(char ch) { switch(ch) { case '

{'

: insertToken(4, -1);

printf( %c\t界限符\n ,ch);

break;