[tzs]

The Ruby stuff apparently isn't bizarre. From what I've read, Ruby creates variables as it encounters an assignment to them when parsing the code. So, when you have

   a = a

in your code, Ruby creates the variable a before it ever tries to actually execute the assignment. If later, when it has finished parsing everything, and starts executing, that statement fails because b is not defined, you still end up with variable a being defined, and since it has not had anything successfully assigned to it, it has a value of nil.

The JavaScript stuff, I think, comes from operator overloading. The plus operator is overloaded to allow adding strings to concatenate them, and it will do type conversion to get compatible types, so "wat"+1 results in the 1 being converted to a string, and then the strings are concatenated. Since the minus operator is not so overloaded, "wat"-1 instead is treated as numerical subtraction. JavaScript allows string to be used as numbers, so "123"-1 gives 122. However "wat" is not a string that represents a number, so gives NaN when forced to be treated as a number, and "wat"-1 is thus NaN.

[lucisferre]

Thanks for that. I was curious the reason, it seems obvious though after an explanation.