`empty?` should be documented more clearly.

[amano-kenji]

repl:1:> (doc empty?)

    function
    boot.janet on line 117, column 1

    (empty? xs)

    Check if xs is empty.

What? Define empty. I thought nil was empty.

[kenaryn]

nil is derived from latin nihil which approximately stands for "no thing". There is no thing (pun intended) like emptyness. Even the cosmic void is filled with reversed Kasimir force (formerly known as dark matter then more recently as dark energy).

I think the Janet doc means "Check if xs has a null valence ( from latin ne ullus, "not one") if I were to use array theory terminology. I know Janet is not based on Array paradigm (unlike a language like Nial) so perhaps Check if xs has a zero dimensionality could be adopted in stead...

... or even "Check if xs has a null length".

[amano-kenji]

Define xs.