ok, i'll bite. why should i prefer join rather than concat in the list
monad. and, moreover, why is this a lambdabot trick?
i suspect that the answer actually has a deep connection to the
'dummies' thread next door. while any program that produces the right
result is correct, there are some that are more correct than others. a
good introductory guide to haskell should lead you in that direction.
reasoning by analogy, for c++, andy koenig's accelerated c++ had a
huge impact on teaching c++ because it didn't start with C or pidgen
c++, but instead required the student to accept that many mechanisms
would be explained later, but that they should be used -now-.
i suspect that being biased towards higher order functions, and
writing new functions such that monads (although the more i learn i
think that should be typeclasses) can take advantage of those
functions, is the skill that needs to be learned / taught. the
equivalent of the central dogma of OO, where it's all about objects
having identity, state , and behavior.
On 12/13/06, Donald Bruce Stewart
ulfn:
On Dec 13, 2006, at 3:54 AM, Yitz Gale wrote:
Nice. Here is something similar:
reverseWords = concat . reverse . groupBy eqsp where eqsp x y = isSpace x == isSpace y
This can be made even nicer using the 'on' function [1]:
reverseWords = concat . reverse . groupBy ((==) `on` isSpace)
[1] http://www.haskell.org/pipermail/libraries/2006-November/006156.html
Lambdabot trick(tm), use 'join' in the [] monad, instead of 'concat'
join . reverse . groupBy ((==) `on` isSpace)
-- Don _______________________________________________ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe