Re: Quiz #65, Principle of Great Surprise, and Array.delete sledgehammer


On Feb 4, 2006, at 3:50 PM, Dave Howell wrote:

I thought I was actually going to enter my first RubyQuiz, but I've spent three times as much time trying to get Ruby to stop surprising me as I have trying to implement my algorithm, and I've had to abandon my effort since I don't have the time to spend. Sigh.

Can somebody explain to me how I'm supposed to delete a *single* element from an array based on equivalence with an object? and get back said array with said element deleted?

In other words....

ar = [1, 2, 3, 8, 15, 15, 8]

ar.delete_one_element!(15)
=> [1, 2, 3, 8, 15, 8]

ar.delete_one_element!(14)
=> [1, 2, 3, 8, 15, 15, 8]

ar.delete_one_element!(nil)
=> [1, 2, 3, 8, 15, 15, 8]

I did find so many different ways of not doing this....

Too enthusiastic....
ar.delete(15)
=> 15
ar
=> [1, 2, 3, 8, 8]

Right results, wrong output...
ar.slice!(ar.index(15))
=> 15
ar
=> [1, 2, 3, 8, 15, 8]

and also surprised me by not handling 'nil' as I wanted...
ar.slice!(ar.index(13))
TypeError: no implicit conversion from nil to integer
from (irb):8:in `slice!'
from (irb):8


I mean, this seems so, er, obvious! "Please find one instance of this object in the array, and return to me the array without that object. If the array doesn't have that object, then just give the array back to me."

Why isn't that the Ruby Way? What am I missing here?

Help?




require 'enumerator'
class Array
def delete_one_element(x = nil)
if block_given?
tester = lambda { |item| yield(item) }
else
tester = lambda { |item| item == x }
end
index_of_element = self.to_enum(:each_index).find { |i| tester.call(self[i]) }
unless index_of_element.nil?
self.delete_at(index_of_element)
end
self
end
end




.

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