表达式计算器，支持四则与括号运算(C++)

#include "Cacluate.h" void Calculate::setString(string str) { clear(); infixString=str; existString=true; } bool Calculate::checkEqual() { string::size_type pos=infixString.size(); if(infixString[pos-1]!='=')//检查等于号 { return false; } char temp_pre=infixString[pos-2]; if((temp_pre<=43&&temp_pre>=42)||temp_pre==45||temp_pre==47)//检查倒数第二个符号是否为运算符 { return false; } return true; } bool Calculate::run(double& answer) { if(!existString) { return false; } if(!analysis()) { return false; } if(!convertInfixToPostfix()) { return false; } if(!calculate(answer)) { return false; } return true; } void Calculate::clear() { existString=false; infixString.clear(); infix.clear(); postfix.clear(); } void Calculate::getPostfix(string& postfixStr) { for(vector<string>::iterator itr=postfix.begin();itr!=postfix.end();itr++) { postfixStr+=(*itr); } } bool Calculate::analysis() { string matchN("0123456789."); char temp_pre; string::size_type pre=0; string::size_type pos=0; string::size_type size=infixString.size(); while(pre<size) { temp_pre=infixString[pre]; if((temp_pre<=57&&temp_pre>=48)||temp_pre==46) { string numStr; pos=infixString.find_first_not_of(matchN,pre); numStr=infixString.substr(pre,pos-pre); pre=pos; infix.push_back(numStr); } else if((temp_pre<=43&&temp_pre>=40)||temp_pre==45||temp_pre==47) { string symbolStr=infixString.substr(pre,1); pre++; infix.push_back(symbolStr); } else { if(temp_pre!=61) { return false; } pre++; } } return true; } bool Calculate::checkBrackets() { string l_brackrt="("; string r_bracket=")"; string ::size_type size=infix.size(); string::size_type pos(0); while(pos!=size) { if(infix[pos]==l_brackrt) { cac_stack.push(infix[pos]); } else if(infix[pos]==r_bracket) { if(cac_stack.empty()) { return false; } if(cac_stack.top()!=l_brackrt) { return false; } cac_stack.pop(); } } if(!cac_stack.empty()) { return false; } return true; } bool Calculate::convertInfixToPostfix() { string num("0123456789."); string symbol("+-*/"); string ::size_type size=infix.size(); string::size_type pos(0); while(pos!=size) { if(infix[pos]=="(") { cac_stack.push(infix[pos]); } if((infix[pos].find_first_of(symbol))!=string::npos) { if(cac_stack.empty()) { cac_stack.push(infix[pos]); } else { switch(compareSymbol(infix[pos],cac_stack.top())) { case gt: cac_stack.push(infix[pos]); break; case le: case eq: postfix.push_back(cac_stack.top()); cac_stack.pop(); while(!cac_stack.empty()) { switch(compareSymbol(infix[pos],cac_stack.top())) { case le: case eq: postfix.push_back(cac_stack.top()); cac_stack.pop(); continue; case er: break; } break; } cac_stack.push(infix[pos]); break; case er: cac_stack.push(infix[pos]); break; } } } if(infix[pos]==")") { while(cac_stack.top()!="(") { postfix.push_back(cac_stack.top()); cac_stack.pop(); } cac_stack.pop(); } if((infix[pos].find_first_of(num))!=string::npos) { postfix.push_back(infix[pos]); } pos++; } while(!cac_stack.empty()) { postfix.push_back(cac_stack.top()); cac_stack.pop(); } return true; } bool Calculate::calculate(double& answer) { while(!cac_stack.empty()) { return false; } string num("0123456789."); string symbol("+-*/"); string ::size_type size=postfix.size(); string::size_type pos(0); while(pos!=size) { if((postfix[pos].find_first_of(num))!=string::npos) { cac_stack.push(postfix[pos]); } if((postfix[pos].find_first_of(symbol))!=string::npos) { double retNum(0); double rightNum=atof(cac_stack.top().c_str()); cac_stack.pop(); double leftNum=atof(cac_stack.top().c_str()); cac_stack.pop(); if(postfix[pos]=="+") { retNum=leftNum+rightNum; } else if(postfix[pos]=="-") { retNum=leftNum-rightNum; } else if(postfix[pos]=="*") { retNum=leftNum*rightNum; } else if(postfix[pos]=="/") { retNum=leftNum/rightNum; } char tmp[15]; sprintf_s(tmp,"%5.5f",retNum); string tmpRet(tmp); cac_stack.push(tmpRet); } pos++; } answer=atof(cac_stack.top().c_str()); } compret Calculate::compareSymbol(string&left,string &right) { if(left=="+"||left=="-") { if(right=="*"||right=="/") { return le; } else if(right=="+"||right=="-") { return eq; } } if(left=="*"||left=="/") { if(right=="+"||right=="-") { return gt; } else if(right=="*"||right=="/") { return eq; } } return er; }