Editing Syntactic sugar/Cons (section)

==== Comma separated list elements ====

We are used to the [[list notation]] <hask>[0,1,2,3]</hask>.
I think many Haskell users are not aware that it is a special notation.
They don't know that it is a replacement for <hask>(0:1:2:3:[])</hask>,
and because of that they also can't derive
that a function for constructing single element list can be written as <hask>(:[])</hask>.

The comma separated list notation <hask>[0,1,2,3]</hask> is very common, but is it sensible?
There are two reasons against:

* The theoretical reason: The intuitive list notation using comma separation requires one comma less than the number of elements, an empty list would need -1 commas, which can't be written, obviously.
* The practical reason: The colon is like a terminator. Each list element is followed by the colon, thus it is easier to reorder the elements of a list in an editor. If you have written <hask>(1:2:3:[])</hask> you can simply cut some elements and the subsequent ':' and then you can insert them whereever you want.


Although the list type has so many special support by the Haskell 98 language,
there is no need for some syntactic support.
The definition

data List a = End | (:) a (List a)

is regular Haskell98 code.
The colon should have precedence below <hask>($)</hask>.
Then a list type can be <hask>List Int</hask> and
a list value can be <hask>1 : 2 : 3 : End</hask>.

Again, this proves the power of the basic features of Haskell98.