1、7、根据常量说明串置于高级语言源程序中时可能出现的错误情况,模仿高级语言编译器对不同错误情况做出相应处理。四、运行结果1、输入如下正确的常量说明串:const count=10,sum=81.5,char1=f,max=169,str1=“h*54 2.4S!AAsj”, char2=,str2=“aa!+h”;输出:count(integer,10)sum(float,81.5)char1(char, f)max(integer,169)str1(string,“h*54 2.4S!AAsj”)char2(char, )str2(string,“aa!+h”)int_num=2; char_
2、num=2; string_num=2; float_num=1.2、输入类似如下的保留字const错误的常量说明串:Aconstt count=10,sum=81.5,char1=f;输出类似下面的错误提示信息:It is not a constant declaration statement! Please input a string again!3、输入类似如下含常量名或常量值错误的常量说明串:const count=10,12sum=81.5,char1=ff,max=0016;12sum(Wrong! It is not a identifier!)char1(Wrong! Th
3、ere are more than one char in .)max(Wrong! The integer cant be started with 0.)int_num=1; char_num=0; string_num=0; float_num=0.4、其他类型的错误处理情况(略)。五、提示本实验重点有三个:一是作为常量名的标识符的识别;二是如何根据“=”后出现的内容来判断常量类型;三是对各种错误的处理。难点是对整型和实型常量的判断必须综合考虑多种可能情况。建议:1、用指针或数组与指针相结合来处理输入的常量说明串;2、对整型和实型常量处理时,重点考虑常数中0的位置。六、分析与讨论1、若考
4、虑用E或e的科学计数法来表示整数和实数,应该如何实现?2、若考虑布尔型常量,且规定其值只能为true或false,应该如何实现?3、如何对手工构造的词法分析程序做进一步的优化,以提高代码质量和运行效率?七代码#includestdio.hctype.h#includestring.hwindows.h#define N 80#define M 16char *p0,*t0,*p1,*t1, *p2,*str,*p3,*t3=const,*digi,*flo;char cha;int ci=0,cf=0,cc=0,cs=0;void main() void measurefw(); void m
5、easure_iden(); void measure_str(); void measure_digit(); void measure_cha(); printf(nInput string: n); p0=(char *)malloc(N*sizeof(char); p1=(char *)malloc(M*sizeof(char); p2=(char *)malloc(M*sizeof(char); p3=(char *)malloc(M*sizeof(char); gets(p0);n measurefw();/* 开始处理输入串 p0 */ while(*(p0)= |*(p0)=,
6、) /*从串p0中取标识符,并将其作为常量名存放到串p1中 */ p0+; if(*(p0)= continue; else measure_iden(); /*p0= if(!isdigit(*p0)&*p0!=)/注意和做字符表示时用和 system(cls printf(n Const data is wrong . Exit ! exit(0); else if(*p0=) /* 处理字符串常量 */ p0+; measure_str(); else if(isdigit(*p0) /* 处理数字 */ measure_digit();) /处理字符常量 measure_cha();
7、if(*p0!; system( printf(n This centence is wrong . Exit ! exit(0); elseint_num=%d; char_num=%d; string_num=%d; float_num=%d.n,ci,cc,cs,cf);void measurefw() while(*p0!) /* 检查输入串是否以开头 */ if(*p0=*t3) t3+;nThis string isnt a const declaration!/ printf(This string is a const declaration!void measure_iden
8、() if (*p0!_(!isalpha(*p0) n Const name is wrong . Exit ! else if (*p0=|isalpha(*p0) t1=p1; while(*p0! *p1=*p0; p1+; *p1=0/ printf(%sn,p0);%s,t1);void measure_str() str=p2; while(*(p0)! *p2=*p0;)/丢了个分号,直接输出String data is wrong. Exitn String data is wrong. Exit ! p2+; *p2= p0+; cs+;(string,%s)n,str);void measure_digit() char *jud; int mark=0; jud=p0; for(;*(jud)!jud+) if(*jud=. mark=1; break; if(mark=0) digi=p2; *p2=*p0; p2+; *p2= ci+;(integer,%s)n,digi); if(mark=1) flo=p2; cf+;(float,%s)n,flo);void measure_cha() if(*(jud+1)= cha=*p0; p0=p0+2; cc+;n char data is wrong. Exit !(char,%c,cha);
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