Expression question from Demonoire project

In the transition function of the Demonoire project there's a line of code that I don't understand (line 10 of the eGlobal event sheet

Transition - > Self.State = "Out" ? 0 : 100

normally i'm used to just putting a number for the opacity of an object, but how does the code work exactly? Does it help animate the opacity?

Its shorthand for:

if Self.State ="Out"

then Transition = 0

else Transition = 100

Very cool. I didn't realize after all this time that you could do it all in one line like that.

It's technical name is the "conditional (ternary) operator" quite a lot of people refer to it as the ternary operator as most languages only have 1 ternary operator. Ternary operator meaning that it contains 3 parts. It's form is:

condition ? thenClause : elseClause

It's all documented in the manual.