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#include#include#include#include#include class CStr private: int nLen; /字符串长度 char *pStr; /字符串首地址public: CStr()nLen=0;pStr=NULL; /不含参数的构造函数CStr(char *str); /含参数的构造函数 CStr(CStr &str); /拷贝的构造函数/CStr()if(pStr)delete pStr; /析构函数 int GetLen()return nLen; /返回字符串的长度CStr Midstr(CStr &str,int nStart,int nLength); /返回指定字符串类中从nStart序号开始nLength长度的字符串CStr Left(CStr &str,int nLength); /返回指定字符串类中从左边开始nLength个字符CStr Right(CStr &str,int nLength); /返回指定字符串类中从右边开始nLength个字符 CStr &Calculate(); /计算该字符串所代表的四则运算的值（内无括号）int CharInStr(char chChar); /判断字符chChar是否在字符串中 double Val();/求字符串代表的数字字符的值 char GetChar(int i)return *(pStr+i);/返回字符串中第i个字符 CStr Str(double val); /将数值表示成字符串的形式CStr &operator=(CStr &);/重载赋值运算符 friend CStr operator+(CStr &str1,CStr &str2)/友元，实现对象的加法 CStr t; t.nLen=str1.nLen+str2.nLen; t.pStr=new char t.nLen+1; strcpy (t.pStr,str1.pStr); strcat(t.pStr,str2.pStr); return t; operator char*()return(char*)pStr; /将字符串类转换成字符数组 friend istream &operator(istream &is,CStr &str)/重载输入运算符 char oristr100; is.getline(oristr,100); CStr in(oristr); str=in; str.GetLen(); return is; friend ostream &operator=0)/赋值nLength个字符 *(t.pStr+nLength)=*(str1.pStr+nLength-); return t; /返回指定字符串类中从左边开始nLength个字符CStr CStr:Left(CStr&str,int nLength) CStr t;CStr str1(str); t.nLen=nLength; t.pStr=new chart.nLen+1; *(t.pStr+-nLength+1)=0; /目的字符串以0结尾 while(nLength=0)/赋值nLength个字符 *(t.pStr+nLength)=*(str1.pStr+nLength-); return t;/返回指定字符串类中从右边开始nLength个字符CStr CStr:Right(CStr &str,int nLength) CStr t;CStr str1(str); t.nLen=nLength; t.pStr=new chart.nLen+1; while(*str1.pStr!=0)str1.pStr+; /移至第一 个字符串尾部 str1.pStr-=nLength;/跳至欲赋值的首地址 *(t.pStr+-nLength+1)=0;/目的字符串以0结尾 while(nLength=0) /赋值nLength个字符 *(t.pStr+nLength)=*(str1.pStr+nLength-); return t;/判断字符chChar是否在字符串中int CStr: CharInStr(char chChar) int pos=0; while(*(pStr+pos)!=0) /循环查找 if(chChar=*(pStr+pos+) return pos;/找到返回其位置 return 0;/求字符串所代表的数字字符的数值double CStr:Val() char *source=pStr; double result=0,multiplier; int pos_in_str=CharInStr(.);/找出小数点的位置if(*pStr=)source+;/如字符串代表的值为负值，指针后移一位if(pos_in_str=0) /字符串中不含小数点if(*pStr=) multiplier=pow(10,nLen-2);else multiplier=pow(10,nLen-1); while(*source!=0) result+=(*(source+)-0)*multiplier;multiplier/=10; else if(*pStr=) /字符串中含小数点 multiplier=pow(10,pos_in_str-3);else multiplier=pow(10,pos_in_str-2); while(*source!=0) if(*source!=.)result+=(*(source)-0)*multiplier; multiplier/=10; source+; if(*pStr=) result=0-result;/含“”时，将得出的值转为负值return result;/将数值表示成对象的形式CStr CStr:Str(double val) char p100; CStr str;int x=0,a=0,i=0,multiplier1;double multiplier2,b;if(val=0)/数值为零时p0=0;p1=0;else if(val=1)/正数时将整数部分和小数部分分开存放，x:小数部分; val:整数部分x=int(val);val-=x;if(x=0)/只有小数部分，整数部分为零pi+=0;pi+=.;multiplier2=0.1;for(;i+) b=val/multiplier2; pi=0+int(b); val-=multiplier2*int(b); multiplier2/=10; if(val=1e-10) /小数部分小于10的-10次方部分舍去pi+1=0;break;else /整数部分和小数部分都有时for(multiplier1=1000000000;multiplier1!=0;multiplier1/=10)/先将整数部分转换为字符pi=0+(x/multiplier1); x-=(x/multiplier1)*multiplier1; if(pi!=0|(a)/寻找数字转换为字符的第一个a+;i+;if(val=0) pi=0; /小数部分为零时（原值为整数时）else/小数部分不为零时pi=.;/增加小数点，指针后移一位i+;multiplier2=0.1; for(;i+) /将小数部分转换为字符b=val/multiplier2;pi=0+int(b);val-=multiplier2*int(b); multiplier2/=10; if(val=1e-10) pi+1=0; break; str=CStr(p); return str;/*char p100;sprintf(p,%.10f,val);CStr res(p);return res;*/ /重载赋值运算符CStr & CStr:operator=(CStr &str) if(pStr) deletepStr; nLen=str.nLen; if(str.pStr) pStr=new charnLen+1; strcpy(pStr,str.pStr); else pStr=0; return *this;/计算该字符串所代表的四则运算的值（内无括号） CStr &CStr:Calculate() CStr buf1,buf2,buf3,buf4,buf5; char opstr6=*/+-; double leftnr; double rightnr; int oppos; int z; long double result;for(int pos_in_opstr=0;pos_in_opstr=0;z-)/*将运算符左边的数字字符取出转换为值*/ if(*(pStr+z)=+)|(*(pStr+z)=-)|(*(pStr+z)=*)|(*(pStr+z)=/)|(*(pStr+z)=) buf1=Midstr(oristr,z+2,oppos-z-2); leftnr=buf1.Val(); z=-1; else if(z=0) buf1=Left(oristr,oppos-1); leftnr=buf1.Val(); for(z=oppos;znLen;z+)/*将运算符右边的数字字符取出转换为值*/ if(*(pStr+z)=+)|(*(pStr+z)=-)|(*(pStr+z)=*)|(*(pStr+z)=/)|(*(pStr+z)=) buf2=Midstr(oristr,oppos+1,z-oppos); rightnr=buf2.Val(); z=nLen; else if(z=nLen-1) buf2=Right(oristr,nLen-oppos); rightnr=buf2.Val(); /对两个数值进行计算，结果在result中 if (opstrpos_in_opstr=+)result=leftnr+rightnr; else if(opstrpos_in_opstr=-)result=leftnr-rightnr; else if(opstrpos_in_opstr=*)result=leftnr*rightnr; else if(opstrpos_in_opstr=/)result=leftnr/rightnr; else if(opstrpos_in_opstr=)result=pow(leftnr,rightnr); /计算后，将结果转换为字符串，然后将左右未运算过的字符串与其连接起来 buf4=Left(oristr,oppos-buf1.nLen-1); buf5=Str(result); buf3=buf4+buf5; buf5=Right(oristr,nLen-oppos-buf2.nLen); *this=buf3+buf5; return *this;/判断输入是否合法，清除空格int CStr:judge() int i,j; CStr str=*this; int flag=1; for(i=0;i=0&*(pStr+i)=9)|*(pStr+i)=+|*(pStr+i)=-|*(pStr+i)=*|*(pStr+i)=/|*(pStr+i)=|*(pStr+i)=.|*(pStr+i)=(|*(pStr+i)=)|*(pStr+i)=) /不存在不合法的字符时 if(i=nLen-1); else if(*(pStr+i)= )/如有空格，去除空格，所有字符向前移一位 j=i; while(*(pStr+j)=*(pStr+j+1); *(pStr+j)=0; i-; nLen-; if(i=nLen-1); else continue; else flag=0; /存在不合法的字符时 for(i=0;inLen;i+) if(*(str.pStr+i)=+|*(str.pStr+i)=-|*(str.pStr+i)=*|*(str.pStr+i)=/|*(str.pStr+i)=) i+; if(*(str.pStr+i)=+|*(str.pStr+i)=-|*(str.pStr+i)=*|*(str.pStr+i)=/|*(str.pStr+i)=) flag=0; /if(flag=0) /coutn 输入的表达式有误，请重新输入。nn; return flag;/友元重载运算符，实现对象的输入ostream &operator(ostream &os,CStr &str)for(int i=0;istr.nLen;i+)if(*(str.pStr+i)=)os-;else os*(str.pStr+i);return os;void main() CStr oristr,strn,buf1,buf2,buf3,buf4,buf5;int z,lastopen;char choice100;cout*; cout*欢迎使用四则运算器*;cout*注意：输入需符合一定规则，运算优先级为 * / + -，另用代替负号*;for(;)cout*;coutoristr; while(oristr.judge()=0) /判断输入是否合法，错误时提示重新输入coutoristr; strn=oristr; while(strn.CharInStr() /判断左括号 for(z=0;z=strn.GetLen();z+) if(strn.GetChar(z)=()lastopen=z;/找最后一个左括号的位置 if(strn.GetChar(z)=) /找到第一个右括号，将左右括号中的字符串取出计算buf4=strn.Midstr(strn,lastopen+2,z-lastopen-1