[Haskell-cafe] Powerset of a set
Albert Y. C. Lai
trebla at vex.net
Mon Sep 14 19:23:44 UTC 2015
On 2015-09-14 02:57 PM, JORGE MALDONADO wrote:
> The powerset of set s is a set containing all subsets of s.
> I need a clue on how to write Haskell code to get the superset of a
> set using direct recursion and list comprehension.
To compute all subsets of x:xs, i.e., "powerset (x:xs) = ?" :
Suppose powerset xs correctly answers you all subsets of xs. How do you
build upon its answer to obtain all subsets of x:xs?
Basically, each subset of xs is also a subset of x:xs, so you want to
include them in your answer for x:xs.
On top of that, for each subset of xs, you can insert x and get a subset
of x:xs, too.
Does this cover all cases?
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