[Haskell-beginners] A Key Part of Functional Programming

[Costello, Roger L.]

Hi Folks,

Richard Bird write on page 91 of his book, "Introduction to Functional Programming using Haskell":

	The datatype of lists is the workhorse 
	of functional programming.

Notice that he does not say that lists are the workhorse of "Haskell." No. He makes a much broader statement. Lists are the workhorse of Haskell and Lisp and Miranda and all the functional languages. Lists are a key part of functional languages.

On page 95 he defines the list concatenation operator:

	(++)		::  [a] -> [a] -> [a]
	[] ++ ys 	=  ys
	(x:xs) ++ ys	=  x : (xs ++ ys)

Then on page 96 he states:

	Once one has come to grips with the definition of ++, 
	one has understood a good deal about how lists work 
	in functional languages. 

Again notice that he does not say that by coming to grips with the definition of ++ one will have a good understanding of how lists work in "Haskell." No. He makes a much broader statement. One will have a good understanding of how lists work in all functional languages. Although the syntax may change, this definition of concatenation is for all functional languages.

Wow! That is so cool.

/Roger