Swift while循环中的逻辑运算符“ AND” /“ OR”

Question

I am new to Swift and computer science in general. In addition to Apple documentation, I'm using Swift Playground on the iPad to supplement my education. Within Swift Playground, the goal of my code is go get my character though a maze. The following code will correctly get my though my maze:

func navigateAroundWall() {
    if isBlockedRight && isBlocked {
        turnLeft()
    } else if isBlockedRight {
        moveForward()
    }  else {
        turnRight()
        moveForward()
    }
}

while !isOnOpenSwitch {
    while !isOnGem && !isOnClosedSwitch {
        navigateAroundWall()
    }
    if isOnGem {
        collectGem()
    } else {
        toggleSwitch()
    }
    turnLeft()
   turnLeft()
}

Here is where my confusion lies:

while !isOnGem && !isOnClosedSwitch {
        navigateAroundWall()
    }

To correctly go through my maze, if my character 'isOnGem' or 'isOnClosedSwitch', my character should not 'navigateAroundWall'. The problem with this is that I don't understand why my logical operator has to to be AND (&&), and not OR (||) to correctly run. Why is 'navigateAroundWall' executed when only one condition is true and the AND operator is used?

Below is an image to help your visualization of the maze.. as you can see there is no instances where my character will be on a gem and on a switch (the tile At the bottom-right corner) at the same time.

Answer 1

This is a simple application of De Morgan's law: not (a or b) equals to not a and not b

In your case when a or b is true you do not want to go to that call. This is therefore equal to the if condition presented.

You could also write it with or but then you need to negate it since you do not want to do it on those conditions.

Answer 2

There are De Morgan's laws that you should know to understand where is your problem. Due to De Morgan's laws NOT(A AND B) is NOT(A) OR NOT(B), NOT(A OR B) is NOT(A) AND NOT(B). So, in your code now you have NOT(A) AND NOT(B) that is equal to NOT(A OR B).