What does the : infix operator do in Haskell?

Question

I\'m reading A Gentle Introduction to Haskell (which is not so gentle) and it repeatedly uses the : operator without directly explaining what it does.

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Answer 1

The : operator in Haskell is the constructor for lists. It 'cons' whatever is before the colon onto the list specified after it.

For instance, a list of integers is made by 'consing' each number onto the empty list, e.g;

The list [1,2,3,4] can be constructed as follows:

• 4 : [] (consing 4 to the empty list)
• 3 : [4] (consing 3 onto the list containing 4)
• 2 : [3,4] (consing 2 onto the list containing 3, 4)
• 1 : [2,3,4] (consing 1 onto the list containing 2,3,4)

giving you;

[1,2,3,4]

Written fully that's;

1 : 2 : 3 : 4 : []