C++实现能四则运算计算器

#include <iostream>
#include <string>
#include <cmath>
#include <deque>
using namespace std;

#define LENGTH 61440 //60KB
bool isNo(char c) //is Number
{
return c >= '0' && c <= '9' || c == '.';
}
bool isSyb(const char* c)//is Symbol
{
return (*c == '+' || *c == '-' || *c == '*' || *c == '/') && strlen(c) == 1; //ver1.2
}
bool isSyb(char c)//is Symbol
{
return c == '+' || c == '-' || c == '*' || c == '/';
}

bool isIlg(char c) //is illegal
{
return !isNo(c) && !isSyb(c) && !(c == '(' || c == ')' || c == ' ');
}

const char* GetSubtext(const char* S,size_t bgn,size_t end) //follow "left-inclusive interval"
{
char* subtext  = new char[end - bgn + 1];
subtext[end - bgn] = '\0';
for (size_t i = bgn; i != end; i++)
subtext[i - bgn] = S[i];
return subtext;
}
const char* calc(const char* S,size_t len)
{
deque<string> words;
bool inNo = false; //door for isNo
//bool inSyb = false; //door for isSyb
size_t NoPos = 0;
//size_t SybPos = 0;
size_t ParPos = 0, ParDep = 0;
for (size_t i = 0; i <= len; i++) //build standard formula
{

if(isIlg(S[i]) && i != len) //formula illegal checking
{
return "The formula is illegal!";
//exit(1);
}

if (isNo(S[i]) && !inNo) //Number postion begin
{
inNo = true;
NoPos = i;
}
if (!isNo(S[i]) && inNo) //Number postion end
{
inNo = false;
words.push_back(GetSubtext(S,NoPos,i));
}

if (isSyb(S[i])/* && !inSyb*/)
{
/*
inSyb = true;
SybPos = i;
*/
words.push_back(GetSubtext(S,i,i + 1));
}
/*
if (!isSyb(S[i]) && inSyb)
{
inSyb = false;
words.push_back(GetSubtext(S,SybPos,i));
}*/

if (S[i] == '(')
{
//inPar = true;
ParDep++;
ParPos = i + 1; //left-inclusive interval
size_t j;
for (j= i + 1; ParDep && j <= len; j++)
{
if (S[j] == '(') ParDep++;
if (S[j] == ')') ParDep--;
}
if (j <= len)
{
string recResult(calc(GetSubtext(S,ParPos,j - 1),strlen(GetSubtext(S,ParPos,j - 1))));
if (recResult == "The formula is illegal!")
return "The formula is illegal!";
else if (recResult == "Parentheses is not match!")
return "Parentheses is not match!";
else
words.push_back(recResult);
}
else
{
//parentheses is not match
return "Parentheses is not match!";
}
i = j; //jump over subtext
}
if (S[i] == ')')
return "Parentheses is not match!";
} //end for

long double tempResult = 0;
static char CtmpResult[50];

//check formula
if (words.size() == 0) return "0."; // 0 element
if (words.size() == 1 ) //1 element
if( !isSyb(words.front().c_str()))
{
strcpy_s(CtmpResult,words.front().c_str());
return CtmpResult;
}
else
return "The formula is illegal!";
if (words.front() == "*" || words.front() == "/")  //front is symble
return "The formula is illegal!";
if (words.front() == "+" || words.front() == "-")
{
if (!isSyb((words.begin() + 1) -> c_str()))
{
words.front() += *(words.begin() + 1);
words.erase(words.begin() + 1); //erase second one
}
else
return "The formula is illegal!";
}
if (isSyb(words.back().c_str()))
return "The formula is illegal!";
for (deque<string>::iterator i = words.begin() + 1; i < words.end(); i++)
{
if ((*i == "*" || *i == "/") && (isSyb((i-1) -> c_str())) && strlen((i-1) -> c_str()))
return "The formula is illegal!";
if ((*i == "+" || *i == "-") && (isSyb((i-1) -> c_str())) && strlen((i-1) -> c_str()))
if(!isSyb(*((i+1) -> c_str())))
{
*(i + 1) = *i + *(i + 1);
i = words.erase(i);
}
else
return "The formula is illegal!";
}

//start calculate
for (deque<string>::iterator i = words.begin(); i != words.end(); i++)
{
//calculate * and /
if (*i == "*")
{
tempResult = atof((i-1) -> c_str()) * atof((i+1) -> c_str());
_gcvt_s(CtmpResult,tempResult,47);//double to string
i = words.erase(i - 1);
i = words.erase(i);
*i = CtmpResult;
}
if (*i == "/")
{
tempResult = atof((i-1) -> c_str()) / atof((i+1) -> c_str());
_gcvt_s(CtmpResult,tempResult,47); //double to string
i = words.erase(i - 1);
i = words.erase(i);
*i = CtmpResult;
}
}
for (deque<string>::iterator i = words.begin(); i != words.end(); i++)
{
//calculate + and -
if (*i == "+")
{
tempResult = atof((i-1) -> c_str()) + atof((i+1) -> c_str());
_gcvt_s(CtmpResult,tempResult,47); //double to string
i = words.erase(i - 1);
i = words.erase(i);
*i = CtmpResult;
}
if (*i == "-")
{
tempResult = atof((i-1) -> c_str()) - atof((i+1) -> c_str());
_gcvt_s(CtmpResult,tempResult,47);//double to string
i = words.erase(i - 1);
i = words.erase(i);
*i = CtmpResult;
}
}

strcpy_s( CtmpResult, words.front().c_str());
return CtmpResult;
}
void main(int argc,char* argv[])
{
if (argc > 1)
{
cout<<argv[1]<<ends<<'='<<ends<<calc(argv[1],strlen(argv[1]))<<endl;
}
else
{
cout<<"请输入公式,如需退出请按CTRL + C。\nVER1.3 design by zuozhiwen.\n";
char S[LENGTH];
while(1)
{
cin.getline(S,LENGTH);
cout<<calc(S,strlen(S))<<endl;
}
}
}