simple calculator homework assignment

Projects Programming
1

I'm following a guy on YT who gave us/me a homework assignment to build a simple calculator. You enter numbers and operator via the serial monitor and also display on LCD. My "calculator" skips the if statement asking is the user entered a "+". I just can't figure out why. Thoughts?

Best,

Tony

#include <LiquidCrystal.h>
int rs=7;
int en=8;
int d4=9;
int d5=10;
int d6=11;
int d7=12;
LiquidCrystal lcd(rs,en,d4,d5,d6,d7);

int firstNum;
int secondNum;
int result;
String operator1;


void setup() {
  // put your setup code here, to run once:
Serial.begin(9600);
lcd.begin(16,2);

}

void loop() {
  // put your main code here, to run repeatedly:
Serial.println("Enter 1st number");
lcd.setCursor(0,0);
lcd.print("Enter 1st number");

while (Serial.available()==0) {
}
firstNum = Serial.parseInt();

lcd.clear();

Serial.println("Enter 2nd number");
lcd.setCursor(0,0);
lcd.print("Enter 2nd number");

while (Serial.available()==0) {
}
secondNum = Serial.parseInt();

lcd.clear();

Serial.println("Enter operator");
lcd.setCursor(0,0);
lcd.print("Enter operator");

while (Serial.available()==0) {
}
operator1 = Serial.readString();

lcd.clear();

if (operator1 == "+") {
result = (firstNum + secondNum);
lcd.setCursor(0,0);
lcd.print(firstNum);
lcd.print(" ");
lcd.print(operator1);
lcd.print(" ");
lcd.print(secondNum);
lcd.print(" ");
lcd.print("=");
lcd.print(" ");
lcd.print(result);


}

//
//if (operator1 = "-") {
//result = (firstNum - secondNum);
//}
//
//if (operator1 = "*"  || operator1 = "x"  || operator1 = "X") {
//result = (firstNum * secondNum);
//}
//
//
//if (operator1 = "/") {
//result = (firstNum / secondNum);
//}
//
//
Serial.print(firstNum);
Serial.print("   ");
Serial.println(secondNum);
Serial.print("   ");
Serial.print(operator1);
//
//

}
2

Serial monitor line ending setting?

3

The response String may include a line feed and/or carriage return, depending on the serial monitor option selected. Better to compare just the first character.

If you are using an AVR based Arduino, avoid using Strings, and use C-strings (zero terminated character arrays) instead. Strings cause unpredictable memory problems and program crashes.

4

Thanks, folks. I dig into it a bit more with your suggestions.

Best,

T