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44 lines
944 B
Markdown
44 lines
944 B
Markdown
# Summing Collections
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Given a hash, `my_hash`,
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```ruby
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my_hash = {
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"one" => 1,
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"two" => 2,
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"three" => 5
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}
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```
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I want to determine the sum of the values in `my_hash`, which should be `8`.
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This is similar to asking for the sum of the values in an array. In fact,
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using `#values` on `my_hash` will leave us with the task of summing the
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values in an array.
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It turns out that to sum the values in an array, all you need is `#inject`
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```ruby
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[1,2,5].inject(:+)
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=> 8
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```
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So, if I want the sum of the values in a hash, such as `my_hash`, then all
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that is needed is
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```ruby
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my_hash.values.inject(:+)
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=> 8
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```
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To take this one step further, let's consider what will happen with an empty
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array. The above approach will produce `nil`. If we want `0` when the list
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is empty, then tell `#inject` to do just that
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```ruby
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[].inject(0, :+)
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=> 0
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```
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[source](http://stackoverflow.com/questions/1538789/how-to-sum-array-of-numbers-in-ruby)
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