On Feb 26, 2007, at 21:27 , P. R. Stanley wrote:
Hi folks in C and C++ world the humble comma is an operator. Is this also the case in Haskell or, is it classed as a function?
Neither; it's syntactic sugar. The formal tuple constructor is (, [,...]) a [b ...] (e.g. (,,) a b c), with (a, b, c) a friendlier syntax for it, just as [a, b, c] is syntactic sugar for a : b : c : [].
In the wikibook they talk about consing new elements onto a list. Does this cons stand for anything meaningful in the English language? For example, is it short for construction or something similar?
It's "construct", but the term was actually borrowed from Lisp. Count yourself lucky Haskell doesn't use the related Lisp terms "car" and "cdr", which are named after registers in some ancient IBM CPU architecture. Haskell went with the saner "head" and "tail" instead.
I'm assuming that the ":" function takes two arguments and returns a newly constructed list which is assigned to the variable holding/ pointing to the old list.
First part correct, second quite wrong --- Haskell doesn't have destructive assignment in the general case. There are special cases, such as IORefs and MVars and TVars, but Haskell puts restrictions on how you go about using such impure operations. -- brandon s. allbery [linux,solaris,freebsd,perl] allbery@kf8nh.com system administrator [openafs,heimdal,too many hats] allbery@ece.cmu.edu electrical and computer engineering, carnegie mellon university KF8NH