Efficient way to get the first found (or a random) key/value of a large hash

ruby-talk
1

a large hash

h = { … }

1. this is inefficient

first_key, first_value = h.keys[0], h.values[0]

also, #1 is not thread-safe right?

is there a #pairs method which returns [[k1,v1], [k2,v2], …} or

something similar?

2. will this be compatible with future ruby?

h.each_pair {|k,v| first_key, first_value = k, v; break}

···

–
dave

2

David Garamond wrote:

a large hash

h = { … }

1. this is inefficient

first_key, first_value = h.keys[0], h.values[0]

also, #1 is not thread-safe right?

is there a #pairs method which returns [[k1,v1], [k2,v2], …} or

something similar?

2. will this be compatible with future ruby?

h.each_pair {|k,v| first_key, first_value = k, v; break}

Hmm, how about:

k,v = h.find { true } # Find first obj for which block is true

Hal

3

David Garamond lists@zara.6.isreserved.com wrote in message news:40025921.4090603@zara.6.isreserved.com…

is there a #pairs method which returns [[k1,v1], [k2,v2], …} or

something similar?

Hash#to_a does just that:

irb(main):003:0> {:a => 1, :b => 2}.to_a
=> [[:a, 1], [:b, 2]]

4

Ville Aine wrote:

David Garamond lists@zara.6.isreserved.com wrote in message news:40025921.4090603@zara.6.isreserved.com…

is there a #pairs method which returns [[k1,v1], [k2,v2], …} or

something similar?

Hash#to_a does just that:

irb(main):003:0> {:a => 1, :b => 2}.to_a
=> [[:a, 1], [:b, 2]]

yes, but converting the whole hash to an array is inefficient (for big
hashes), that’s why he doesn’t want to use this.