Are there any general guidelines on when a “Set” should be used and when
a
“Hash” should be used. Are there any limitations to “Set”
Kiran K.
SunRaySon wrote:
Are there any general guidelines on when a “Set” should be used and when a
“Hash” should be used. Are there any limitations to “Set”
A Set is similar to an Array - the two major differences are that a Set
is unordered (because it’s implementation is based on a Hash) and that a
Set contains every element only once (i.e. if you add an element which
is already there, the Set won’t change).
You should use a Hash if you have a dictionary-like structure (i.e. key
=> value pairs) and a Set/Array if you have single objects. You can
think about a Set as a Hash where every value is nil - i.e. you can
represent a Set with a Hash but it makes no sense if you are not using
any values at all. In this case you should use a Set.
I hope this answers your question…
Cheers,
Peter
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Thanks for your response. I think now the differences and similarities
between Set, Hash and Array are clear to me. But with respect to memory
consumption which one of among the following is better:
s = Set.new([1,2,3])
h = { 1=>nil, 2=>nil, 3=> nil}
On Sun, 18 Feb 2007, SunRaySon wrote:
Thanks for your response. I think now the differences and similarities
between Set, Hash and Array are clear to me. But with respect to memory
consumption which one of among the following is better:s = Set.new([1,2,3])
h = { 1=>nil, 2=>nil, 3=> nil}
nearly the same - set, in ruby, happens to be built on top of hash.
-a
It should be the same as a Set is implemented as a Hash with every value
being true. Storing true and storing nil uses the same amount of
memory.
Honestly, it doesn’t matter. Use which ever is semantically correct; if
you need to store values with the keys then use a Hash, if you don’t
then use a Set.
Dan