void setup() {
  Serial.begin(9600);
}

void loop() {
  //Serial.read();
  //Serial.parseFloat();
  //Serial.parseInt();
  //Serial.available();

  Serial.println("skriv inn et regnestykke");

  while (!Serial.available());  //samme som (Serial.available == 0){}
  float number1 = Serial.parseFloat();

  while (!Serial.available());
  char op = Serial.read();
  while (op != '+' and op != '-' and op != '*' and op != '/') {
    op = Serial.read();
  }

  while (!Serial.available());
  float number2 = Serial.parseFloat();

  float ans = calculate(number1, op, number2);
  printCal(number1, op, number2, ans);

}


float calculate(float n1, char op, float n2) {
  float ans = 0;
  if (op == '+') {
    ans = n1 + n2;
  }
  else if (op == '-') {
    ans = n1 - n2;
  }
  else if (op == '*') {
    ans = n1 * n2;
  }
  else if (op == '/') {
    if (n2 != 0) {
      ans = n1 / n2;
    }
    else {
      Serial.println("Kan ikke dele på 0");
    }
  }
  return ans;
}

void printCal(float n1, char op, float n2, float ans) {
  Serial.print(n1);
  Serial.print(" ");
  Serial.print(op);
  Serial.print(" ");
  Serial.print(n2);
  Serial.print(" = ");
  Serial.println(ans);
}