User:JulienDethurens/Essays/Pseudo ternaries

If you're reading this, you almost certainly know about the and and or operators. These are useful in if statements to combine boolean expressions and manipulate them. But did you know they could also be useful even outside of if statements?

When you use the and and or operators, you probably think of them in the following way:

• and returns true if both values are neither false nor nil.
• or returns true if any of the values is neither false nor nil.

However, that's not exactly how they work. This is how they really work:

• and returns the first value if it is false or nil. Otherwise, it will return the second value.
• or returns the first value if it is neither false nor nil. Otherwise, it will return the second value.

These definitions might sound weird to you, but think about it:

true and true will not return the first value, because it is neither false, nor nil, and will therefore return the second value. false or true will not return the first value, because it is false, and will therefore return the second value.

You can try this with any combination, and it will still correspond to the definitions you previously used. But there are some small difference...

What does true and 5 return? Remember, everything other than nil and false is considered as true. Therefore, this would return true? No! It would return 5! Why? Well, because the first value is nor false, nor nil, and, therefore, the second value, 5, is returned.

Suppose you wanted to print "Hello" if a BoolValue's value is true, and print "Bye" otherwise. You would probably do it this way:

if boolvalue.Value then
	print("Hello")
else
	print("Bye")
end

But you can make that a lot shorter by using what you have just learned. Look at this:

print(boolvalue.Value and "Hello" or "Bye")

That code does exactly the same thing as the previous code. But how does it work? I will explain that, don't worry:

The code checks if the BoolValue's value is true. If it is, the and operator will therefore return the second value, "Hello". Then, the code left will be "Hello" or "Bye". "Hello" being nor false, nor nil}, it will be returned and therefore, the print function will print "Hello". But, what would happen if the BoolValue's value was false? Let's think about it: the code would evaluate false and "Hello" or "Bye", which would be reduced to false or "Bye", as the first value is indeed false. And since the first value is false, that would return the second value, "Bye".

The previous example used the and and the or operators, but you could also make one that only uses the or operator. Here is an example:

print(a or b)

If a is nil or false, then the value printed will be b. Otherwise, it will be a. This allows you to do many things, like creating optional arguments for functions without having to use if statements. The same thing can be done by using the and operator, though it is not as useful.

You can do lots of things by cleverly manipulating the and and or operators. Many players call this "ternaries", but it is not really ternaries, as it is just clever use of the and and or operators.

Other forms

There are other forms of pseudo ternaries than just using the and and or operators.

An example would be the following:

({[true]=x, [false]=y})[condition]

You can just replace condition by the condition, x by the value you want to get if condition is true and y by the value you want to get if condition is false. However, this method will only consider the value true as being true and the value false as being false. If condition evaluates to anything else than true or false, the value you will get will be nil. If you don't want this to happen, you can just use the not keyword twice in front of the condition to convert it to a boolean without changing its meaning.