class Hash
def hash_revert
hash_new = Hash.new
self.each {|key,value|
if not hash_new.has_key?(key) then hash_new[value] = key end
}
return hash_new
end
end
h = {2=>“a”, 1=> “b”, 3 =>“a”, 4=> “a”, 5 => “b”, 6=>“c”}
p h.hash_revert #–> {“a”=>4, “b”=>1, “c”=>6}
class Hash
def hash_revert
hash_new = Hash.new
self.each {|key,value|
if not hash_new.has_key?(key) then hash_new[value] = key end
}
return hash_new
end
end
h = {2=>“a”, 1=> “b”, 3 =>“a”, 4=> “a”, 5 => “b”, 6=>“c”}
p h.hash_revert #–> {“a”=>4, “b”=>1, “c”=>6}
or Should I get this ??
=> {“a”=>2, “b”=>1, “c”=>6}
Because HASH is working like “Set” ??
many thanks in advance,
salai.
In Ruby 1.9, hashes keep the order of input. Before Ruby 1.9, the order
is “random” - so it’s not guaranteed which will be the first key that
you will see with ‘each’.
if not hash_new.has_key?(key) then hash_new[value] = key end
Because HASH is working like “Set” ??
many thanks in advance,
salai.
In Ruby 1.9, hashes keep the order of input. Before Ruby 1.9, the order
is “random” - so it’s not guaranteed which will be the first key that
you will see with ‘each’.
As far as I can see salai does not want to reverse the order of
elements but rather the key value relationship.
Salai, it really depends on the requirements. Here’s another valid
variant:
class Hash
def hash_revert
r = Hash.new {|h,k| h[k] = []}
each {|k,v| r[v] << k}
r
end
end
But the two are not the same thing. Pastie is a nice pastebin
service, for sure (I typically use it myself when I don’t need the
features gist has to offer)
But codepad.org actually executes the code pasted in. That is what is
neat about it.
The answer can be different (and most likely will be) under 1.8 and 1.9
in
1.8 order is not guaranteed - but in 1.9 it is (order of insertion into
the
hash) and therefore under 1.9 you will get the second option and
apparantly
under 1.8 you get your first.
)