From: Michael McGreevy <ruby-forum.com@...>
Date: 2006-01-26T20:22:53+09:00
Subject: Hash with array as value type

Hello all,

I would like to store arrays in a hash, indexed by a string key.  I
would like to have the hash create an empty array as the default value,
when it sees a new key, something like the code involving "hash1" below.
However, this code is giving some strange results -- it claims that the
hash is empty, even though there is an array stored in it, and I can
then retrieve that array.

I am new to ruby, so maybe I am just doing something stupid (... I am
not sure about that "Hash.new( [] )" for example... )

Can anyone explain these results?

Thanks.

CODE:

#!/usr/bin/ruby


hash1 = Hash.new( [] )
hash1["hello"].push(1.0)
hash1["hello"].push(2.0)
$stderr.write "hash1.size() = #{hash1.size()}\n"
$stderr.write "hash1.empty() = #{hash1.empty?()}\n"
$stderr.write "hash1[\"hello\"].size() = #{hash1["hello"].size()}\n"
$stderr.write "hash1[\"hello\"] = #{hash1["hello"]}\n"

hash2 = {"hello" => [1.0,2.0]}
$stderr.write "\nhash2.size() = #{hash2.size()}\n"
$stderr.write "hash2.empty() = #{hash2.empty?()}\n"
$stderr.write "hash2[\"hello\"].size() = #{hash2["hello"].size()}\n"
$stderr.write "hash2[\"hello\"] = #{hash2["hello"]}\n"


OUTPUT:

hash1.size() = 0
hash1.empty() = true
hash1["hello"].size() = 2
hash1["hello"] = 1.02.0

hash2.size() = 1
hash2.empty() = false
hash2["hello"].size() = 2
hash2["hello"] = 1.02.0




VERSION:
ruby 1.8.3 (2005-09-21) [i686-linux]

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