A line of code that i dont understand?

Using Arduino Programming Questions
1

I am trying to make an Arduino Based calculator that just works with a Keypad, Arduino Uno board and a LCD screen. I found a code online and i tried to understand the code yet i diditn quite understand this part. Can anyone help?

second == 0 ? lcd.print("Invalid") : total = (float)first / (float)second;

2 
 if (second == 0)
    lcd.print("Invalid") ;
else
    total = (float)first / (float)second;
3

Ternary operator.

4

I think that's about one of the worst examples of use/abuse of the conditional operator I could think of. Sure it's legal C, but IMHO it adds nothing to readability and only serves to obfuscate. Added to that one of the expressions has a side effect (printing to the LCD).

No wonder the OP was confused...

Normally you'd see it replacing code like this...

if (a >= b)
{
  max = a;
}
else
{
  max = b;
}

Which you can write more compactly as...

max = (a >= b) ? a : b;

Edit: It's A ternary operator (the only one C has) and not THE ternary operator. Ternary just means 3 arguments, as compared to the more usual binary (two arguments, +, *, > etc) and unary (!, ~, etc) that we are used to.

5

I try to do it But now still confused

6

geosixs:
I try to do it But now still confused

Confused about what?

7

acanyasar:
I am trying to make an Arduino Based calculator that just works with a Keypad, Arduino Uno board and a LCD screen. I found a code online and i tried to understand the code yet i diditn quite understand this part. Can anyone help?

second == 0 ? lcd.print("Invalid") : total = (float)first / (float)second;

This is just code that produces an error when you try to divide by 0. If you do you get the reply “Invalid”.

Edit to fix autocorrect

8

Since you cannot share something amongst nothing, division by zero is not allowed.

9

geosixs is NOT the OP