sic-xe-assembler/infix.cpp at master · adi1998/sic-xe-assembler · GitHub

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#include <bits/stdc++.h>

using namespace std;

class EvaluateString{
public:
  int getResult();
  EvaluateString(string data);
private:
  string storedData;
  int index;
  char peek();
  char get();
  int term();
  int factor();
  int number();
};

EvaluateString::EvaluateString(string data){
  storedData = data;
  index=0;
}

int EvaluateString::getResult(){
  int result = term();
  while(peek()=='+' || peek() == '-'){
    if(get() == '+'){
      result += term();
    }else{
      result -= term();
    }
  }
  return result;
}

int EvaluateString::term(){
  int result = factor();
  while(peek() == '*' || peek() == '/'){
    if(get()=='*'){
      result *= factor();
    }
    else{
      result /= factor();
    }
  }
  return result;
}

int EvaluateString::factor(){
  if(peek() >= '0' && peek() <= '9'){
    return number();
  }
  else if(peek() == '('){
    get();
    int result = getResult();
    get();
    return result;
  }
  else if(peek()=='-'){
    get();
    return -factor();
  }
  return 0;
}

int EvaluateString::number(){
  int result = get() - '0';
  while(peek() >= '0' && peek() <= '9'){
    result = 10*result + get()-'0';
  }
  return result;
}

char EvaluateString::get(){
  return storedData[index++];
}

char EvaluateString::peek(){
  return storedData[index];
}