On Aug 6, 2009, at 3:22 PM, Nik wrote:
>
> Hello, I have this big array of hashes:
> A =[ h0, h1, h2, ..., hn]
> some hi's' :cue key is true, others' is false.
> e.g.,
> h1[:cue] = false
> h2[:cue] = false
> h3[:cue] = true
> h4[:cue] = false
> h5[:cue] = true
> ...
> hn[:cue] = ...
>
> Again, these hashes are in an array, A.
>
> Now, I'd like to group them into smaller arrays whose last item has a
> true cue
> so
> A' = [ [h1, h2, h3], [h4, h5], ... , [...] ]
>
> Is there a built-in method to cook this up?
> If not, what combination of methods might you think would work most
> efficiently?
>
> Thank You
Well, this seems to be a tasty dish. I took some liberty with your
minimal spec, but you should see the first test for the usage that
maps to your example.
#!/usr/bin/ruby -w
class Array
def split_when
result = [[]]
each do |element|
result[-1] << element
if block_given? ? yield(element) : element
result << []
end
end
result.pop if result.last.empty?
result
end
end
if File.expand_path($0) == File.expand_path(__FILE__)
require 'test/unit'
class SplitWhenTest < Test::Unit::TestCase
def setup
h1 = { :cue => false }
h2 = { :cue => false }
h3 = { :cue => true }
h4 = { :cue => false }
h5 = { :cue => true }
@ary = [ h1, h2, h3, h4, h5 ]
@expected = [ [h1, h2, h3], [h4, h5] ]
end
def test_example_from_email
assert_equal @expected, @ary.split_when {|e| e[:cue]}
end
def test_simple
original = [ false, true, false, false, true, true, false,
true, false, true, false ]
expected = [[false, true],[false, false, true],[true],[false,
true],[false, true],[false]]
assert_equal expected, original.split_when, "no block"
assert_equal expected, original.split_when {|e|e}, "simple block"
end
end
end
__END__
:code/ruby $ ./array_split_when.rb
Loaded suite ./array_split_when
Started
..
Finished in 0.000585 seconds.
2 tests, 3 assertions, 0 failures, 0 errors
-Rob
Rob Biedenharn http://agileconsultingllc.com
[email protected]
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