///////    File CalcEng.C    ///////
#include <math.h>    // for pow
#include  "CalcEng.h"

const char* CalcEng::keys = "+-*/=^NnAaCcQq";

CalcEng::CalcEng()
{   allclear();  }

void CalcEng::allclear()
{    ans = arg = 0.0; 
     argcnt = 1;
     err_flag = 0;
     op = '=';
}

void CalcEng::operate(char nc)
{    switch( nc )
     {    case 'A':  // All Clear 
          case 'a':  allclear(); return;
          case 'N':  // Sign change 
          case 'n':  if ( argcnt == 1 ) ans = -ans;
                     else arg = -arg;
                     return;
          case 'C':  // Clear
          case 'c':  if ( err_flag ) err_flag = 0;
                     else
                     {    if ( argcnt == 1 ) ans = 0.0, op = '=';
                          else { arg = 0.0; argcnt = 1;}
                     }
                     return;
          default:   // +-*/=
                     compute();
                     op = nc;       // new opcode
     }
} 

void CalcEng::operand(double in) 
{   if ( op == '=' )
        ans = in;
    else  // if (argcnt == 1) not needed
    {   arg = in;
        argcnt = 2;
    }
}

void CalcEng::compute()
{  if ( argcnt == 2 )
   {  switch( op )
      {   case '+':  ans += arg; break;
          case '-':  ans -= arg; break;
          case '*':  ans *= arg; break;
          case '/':  ans /= arg; break;
          case '^':  ans = pow(ans, arg); break;
      }
      argcnt = 1;
   }
}