From: "Matthew K. Williams" <matt@...>
Date: 2009-11-20T03:46:27+09:00
Subject: Re: Ternary Operator and Arrays

On Fri, 20 Nov 2009, Felix Dominguez wrote:

> Given:
> ary = Array.new
> some_hash = {'a' => 1, 'b' => 2, 'c' => 3}
> another_array = ['a', 'c']
>
> Then:
> another_array.each do |x|
>   ary <<  some_hash.has_key?(key) ? ' ' : some_hash[key]
> end
>
> Expected:
> ary should be [1, ' ', 3]
>
> Actual:
> [true, false, true]
>
> Question:
> Why does that happen?
>

You need parenthesis around the ternary operation.

The reason being is that << has a higher precedence than ?:, so it 
evaluates just the some_hash.has_key?(key), giving a true or a false 
value.

In general, while parenthesis are often optional in Ruby, if you're not 
sure how something works (or it's not clear), parenthesis are your friend.

Matt