A tuple can have any number of elements. (1,2) is a 2-tuple. (1,2,3) is a 3-tuple. (x:xs) and (x,y) are differently typed: xs must be a list of the type of x, while y can be any type. (x:xs) is not a tuple. It is a list by definition.

On Wed, Feb 24, 2016 at 2:45 AM Imants Cekusins <imantc@gmail.com> wrote:

Hello Xiao,

(one_element) -- is evaluation
(element,element,...) -- is tuple

(1:[2]) -- [1,2] because it is one "array element"
(1,2) -- is a tuple because there are 2 elements
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