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Is it appropriate to use integers as keys in a Ruby hash?
Every example from documentation shows a string or symbol being used as a key, but never an integer.
Internally, would integers somehow get converted to strings? I have seen some conflicting information on the subject.
In other words, is there any significant disadvantage to using integer keys to a hash?
719
An explanation, why there are no examples with integers as Hash-keys. Hash-keys have (most of the times) a meaning. It may be an attribute name and its value (e.g. :color => 'red' ...). When you have an integer as a key, your semantic may be 'first, second ...' (1).
The most commonly used method for hashing integers is called modular hashing: we choose the array size M to be prime, and, for any positive integer key k, compute the remainder when dividing k by M. This function is very easy to compute (k % M, in Java), and is effective in dispersing the keys evenly between 0 and M-1.
An integer key just means you assign a value to an integer (i.e. your name is just an integer).
The key helps identify the data and operates as an input to the hashing function, while the hash code or the integer is then mapped to a fixed size. Hash tables support functions that include the following: insert (key, value) get (key)
Others looking at the answers here might find it interesting to know that an exception happens when you use integers as symbol keys in a Ruby hash {symbol: value}
hash = {1: 'one'} # will not work hash = {1 => 'one'} # will work Requested Explanation:
The simplest answer for why the first example fails is probably that to_sym is not a method that's been implemented for Fixnum integers.
To go more in depth to maybe explaining why that is, one of the main benefits to using symbols is that two symbols are in fact "the same object". Or at least they share the same object ids.
:foo.object_id == :foo.object_id => true Strings that are the same do not share the same objects, and therefore do not share the same object ids.
"foo".object_id == "foo".object_id => false Like symbols, Fixnum integers that are the same will have the same object ids. Therefore you don't really need to convert them into symbols.
one = 1 => 1 uno = 1 => 1 one.object_id => 3 one.object_id == uno.object_id => true If you love us? You can donate to us via Paypal or buy me a coffee so we can maintain and grow! Thank you!
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