2014-03-17续昨天的代码

来源：互联网发布：华中博盈软件编辑：程序博客网时间：2024/06/18 12:11

今天早了个起,想要写完昨天的代码,万幸,刚才写完了,初步测试了一下,基本功能是有,不知道有什么bug,等会要提交,现在再从头分析一遍,找找问题

要求:对以'#'结束的标准输入进行词法分析

例如,对源程序 x:=5; if (x>0) then x:=2*x+1/3; else x:=2/x; #
经词法分析后输出如下序列：
（10,’x’）(18, :=) (11,5) (26, ;) (2, if ) (27,( )…… ( 注:前面为词法记号,后面是词法单元)

详细的表在下面,这是题目的要求,换了其他的表也是一样的

词法单元词法记号词法单元词法记号
for   1 :     17
if   2 :=   18
then   3   <   20
else   4 <>   21
while   5 <=   22
do   6   > 23
letter(letter+digit)*10 >=   24
digit digit* 11 =   25
+ 13 ;   26
- 14 ( 27
* 15 )   28
/ 16 # 0
下面是源代码,前面的函数都是很简单的,主要看看主函数的逻辑,有没有错,我等一会要发给老师了!

#include <stdio.h>#include <string.h>char *keyword[6] = {"for", "if", "then", "else", "while", "do"};//keywords arrayint kwlength[6] = {3, 2, 4, 4, 5, 2};                           //keywords' length arrayint pos = 0;                                 //position pointerchar s[256];                                  // input string saved in s[]char new[32];                                //buffer to produce substringchar *substring(char *src, int pos, int length){//get substring    for(int i = 0; i < length; i++){new[i] = s[pos + i];    }    new[length] = '\0';    return new;}int isLetter(char c){                                //is a letter or not    if(c < 'A' || c > 'z' || (c > 'Z' && c < 'a'))return 0;    return 1;}int isNumber(char c){                                //is a number or not    if(c > '9' || c < '0')return 0;    return 1;}int readKeyword(){                                //read keyword    for(int i = 0; i<6; i++){int eq = strcmp(keyword[i], substring(s, pos, kwlength[i]));if(eq == 0){    if(isLetter(s[pos + kwlength[i]]) || isNumber(s[pos + kwlength[i]]))return 0;    printf("(%d, %s)\n", i, keyword[i]);    pos += kwlength[i];    return 1;}    }    return 0;}int readID(){                       //read identifier    if(!isLetter(s[pos]))return 0;    int old_pos = pos;    pos++;    while(isLetter(s[pos]) || isNumber(s[pos])){pos ++;    }    printf("(10, %s)\n", substring(s, old_pos, pos - old_pos));    return 1;}int readNum(){                                                //read number    if(!isNumber(s[pos]))return 0;    int old_pos = pos;    pos ++;    while(isNumber(s[pos])){pos ++;     }    if(s[pos] == '.'){pos ++;while(isNumber(s[pos])){    pos ++;}    }    printf("(11, %s)\n", substring(s, old_pos, pos - old_pos));}int readSymbol(){                                              //read symbol    switch(s[pos]){case '+':    pos ++;    printf("(13, +)\n");    return 1;case '-':    pos ++;    printf("(14, -)\n");    return 1;case '*':    pos ++;    printf("(15, *)\n");    return 1;case '/':    pos ++;    printf("(16, /)\n");    return 1;case ':':    pos ++;    printf("(17, :)\n");    return 1;case '<':    pos ++;    printf("(20, <)\n");    return 1;case '>':    pos ++;    printf("(23, >)\n");    return 1;case '=':    pos ++;    printf("(25, =)\n");    return 1;case ';':    pos ++;    printf("(26, ;)\n");    return 1;case '(':    pos ++;    printf("(27, ()\n");    return 1;case ')':    pos ++;    printf("(28, ))\n");    return 1;case '#':    pos ++;    printf("(0, #)\n");    return 1;default:    return 0;    }}int readSymbol2(){                                          //read 2-char symbol    if(s[pos] == '<' && s[pos + 1] == '>'){pos += 2;printf("(21, <>)\n");return 1;    }    if(s[pos] == '<' && s[pos + 1] == '='){pos += 2;printf("(22, <=)\n");return 1;    }    if(s[pos] == '>' && s[pos + 1] == '='){pos += 2;printf("(24, >=)\n");return 1;    }return 0;}int isBlank(char c){                                        //is blank or not    if(c == ' ' || c == '\t')return 1;    return 0;}

int readBlank(){                                            //read blanks    if(isBlank(s[pos])){pos ++;while(isBlank(s[pos])){    pos ++;}return 1;    }    return 0;}

/*主函数的工作比较简单,将s[]中的字符一个一个拿出来判断

判断前,先将空格和制表符吞了,先判断关键字,再判断id,再判断数字,再判断二目运算法,最后是一目运算符,

如果,都判断了一遍,没有得到肯定的答案,说明这个字符不是规范输入,则提示用户并退出;

当判断到结束符'#'后,将它也分析,然后程序结束

*/int main(){    printf("INFORM:This is a simple program,please do not input unsupported chars.\n");    printf("so input your source code really carefully:\n");    gets(s);    printf("here is the analyzation result:\n");    while(s[pos] != '#'){readBlank();if(s[pos] != '#')    if(readKeyword())continue;if(s[pos] != '#')    if(readID())continue;if(s[pos] != '#')    if(readNum())continue;if(s[pos] != '#')    if(readSymbol2())continue;if(s[pos] != '#')    if(readSymbol())continue;if(s[pos] != '#'){    printf("sorry, you break the rule, program exit!\n");    return -1;}    }    printf("(0, #)\n");    return 1;}

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