编写词法分析程序

Note：

这学期修了严厉的Mr.J的编译原理，不定期更新笔记！
欢迎指正！

TEST 语言的词法规:

• 标识符：字母打头，后接任意字母或数字

• 保留字：标识符的子集，包括：if,else,for,while,do, int,write,read，

• 无符号整数：由数字组成，但最高位不能为0，允许一位的0，

• 分界符：(、)、;、{、}

• 运算符：+、-、*、/、=、<、>、>=、<=、!=、==

• 注释符：/* */

  ---

正则表达式：

• 标识符：        ( a|b|……|z|A|B……|Z )( 0|1|……|9| a|b|……|z|A|B……|Z )*

• 保留字：        标识符的子集

• 无符号整数： ( (1……|9 )( 0|1|……|9)* )|0

• 分界符：        ( | ) | ; | { | }

• 运算符：        + | - | * | / | = | < | > | >= | <= | != | ==

• 注释符：        /* (other)* */
  

  ---

NFA

DFA

将NFA确定化之后得到的DFA

程序测试

依据DFA编写词法分析程序

• 测试数据:

/*This a test program.*/
int abc;
int 123;
int A$@;
int i;
int n;
int b,c;
int 2a;
int a2;
read n;
n = 012345;
for (i=1;i<=n; i= i+1)
{ 
abc=abc+i;
}
if (!n) b = b+c;
/*The loop ended
write abc;
}

• 测试结果:

• 分词结果：
  
  

  ---

SourceCode

#include<stdio.h>
#include<ctype.h>
#include<string.h>
#define sum 8
FILE *fin, *fout;
char Dword[10] = "!><=";
char Infile[300], Outfile[300];
char Sword[50] = "+-*(){};";
char *keyword[sum] = { "if", "else", "for", "while", "do", "int", "read", "write" };
int test()
{
    char ch, Buff[40];
    int flag = 0, n, line = 1;
    int m = 0;
    printf("Name of Pro:");
    scanf("%s", Infile);
    printf("Name of Outfile:");
    scanf("%s", Outfile);
    if ((fin = fopen(Infile, "r")) == NULL)
    {
        printf("\nPro file open error！\n");
        return (1);
    }
    if ((fout = fopen(Outfile, "w")) == NULL)
    {
        printf("\nOutfile open error！\n");
        return (2);
    }
    ch = getc(fin);
    while (ch != EOF)
    {
        m = 0;
        memset(Buff, 0, 40);

        while (ch == ‘ ‘ || ch == ‘\n‘ || ch == ‘\t‘)
        {
            if (ch == ‘\n‘)
            {
                line++;
            }
            ch = getc(fin);
        }
        if (isalpha(ch))
        {
            while (isalpha(ch) || isdigit(ch))
            {
                Buff[m] = ch;
                m++;
                ch = getc(fin);
            }
            n = 0;
            while ((n < sum) && strcmp(Buff, keyword[n]))
            {
                n++;
            }
            if (n < sum)
            {
                fprintf(fout, "%s\t%s\n", "ID", Buff);
            }
            else
            {
                fprintf(fout, "%s\t%s\n", Buff, Buff);
            }
        } 
         else if (isdigit(ch))
        {
            if (ch == ‘0‘)
            {
                Buff[0] = ‘0‘;
                Buff[1] = ‘\0‘;
                fprintf(fout, "%s\t%s\n", "NUM", Buff);
                ch = getc(fin);
            }
            else
            {
                while (isdigit(ch))
                {
                    Buff[m] = ch;
                    m++;
                    ch = getc(fin);
                }
                Buff[m] = ‘\0‘;
                fprintf(fout, "%s\t%s\n", "NUM", Buff);
            }
        }
        else if (strchr(Sword, ch) > 0)
        {
            Buff[0] = ch;
            Buff[1] = ‘\0‘;
            ch = getc(fin);
            fprintf(fout, "%s\t%s\n", Buff, Buff);
        }
        else if (strchr(Dword, ch) > 0)
        {
            Buff[0] = ch;
            ch = getc(fin);
            if (ch == ‘=‘)
            {
                Buff[1] = ch;
                Buff[2] = ‘\0‘;
                ch = getc(fin);
                fprintf(fout, "%s\t%s\n", Buff, Buff);
            }
            else
            {
                Buff[1] = ‘\0‘;
                if (Buff[0] == ‘!‘)
                {
                    printf("Line %d\t%s\t%s\n", line, "ERROR:", Buff);
                }
                else
                {
                    fprintf(fout, "%s\t%s\n", Buff, Buff);
                }
            }
        }
        else if (ch == ‘/‘)
        {
            ch = getc(fin);
            if (ch == ‘*‘)
            {
                char ch1;
                ch1 = getc(fin);
                while (true)
                {
                    if (ch1 == EOF)
                    {
                        printf("Line %d\t%s\tNote does‘t match!\n", line,"ERROR:" );

                        break;
                    }
                    ch = ch1;
                    ch1 = getc(fin);
                    if (ch == ‘*‘&&ch1 == ‘/‘)
                    {
                        break;
                    }
                }
                ch = getc(fin);
            }
            else
            {
                Buff[0] = ‘/‘;
                Buff[1] = ‘\0‘;
                fprintf(fout, "%s\t%s\n", Buff, Buff);
            }
        }
        else
        {
            Buff[0] = ch;
            Buff[1] = ‘\0‘;
            ch = getc(fin);
            flag = 3;
            printf("Line %d\t%s\t%s\n", line, "ERROR:", Buff);
        }
    }
    fclose(fin);
    fclose(fout);
    return(flag);
}

void main()
{
    int flag = 0;
    flag = test();
    if (flag > 0)
    {
        printf("Compile Error\n");
    }
    else
    {
        printf("No Error\n");
    }
}