Hi –
On Thu, 23 Nov 2006, Jason M. wrote:
I thought I was going to get to contribute, but then I got stuck. I
installed the latest ruby, wrote a quick program that I thought would do it,
and it didn’t. So I expanded on the program, trying to figure out what was
going on, and now it’s 20 lines long(mostly puts) and I still don’t get
something (Beware - the single most basic code ever follows - it was
originally much nicer but then I got to trying to debug)
There are a few cobwebs you can clear 
a = Array.new
a = %w{test test2 test3}
You’re using the identifier ‘a’ twice. The first use is discarded.
You might as well do:
a = 1000
a = %w{ test test2 test3 }
The second assignment clobbers the first, with respect to the
variable.
puts a
aSize = a.size
b = Array.new
b = %w{test3 nil test2 test}
Do you really want the string “nil” there, as opposed to the object nil?
bSize = b.size
puts ‘size of b:’ + bSize.to_s
puts b
puts ‘size of a:’ + aSize.to_s
if aSize = bSize
You mean:
if aSize == bSize
aSorted= a.sort!
bSorted= b.sort!
This is OK if everything in both arrays is sortable, but they may not
be:
[1,2,nil,3].sort # => ArgumentError
You can’t compare nil to an integer, nor a string to an integer, etc.,
so an array with mixed objects like that can’t sort.
Here’s another way to go about it. I imagine someone will come along
with a slicker and/or more efficient implementation of the method, but
for what it’s worth, here’s mine:
require ‘test/unit’
module EnumerableAddons
def count(element)
find_all {|e| e == element }.size
end
def equal_to(other)
all? {|e| other.count(e) == count(e) }
end
end
class ArrayComparisonTest < Test::Unit::TestCase
def setup
@a = [1,2,3,4,nil,“hi”].extend(EnumerableAddons)
@b = [2,3,nil,4,“hi”,1].extend(EnumerableAddons)
end
def test_same
assert(@a.equal_to(@b))
end
def test_duplicate
@a << 1
assert(!@a.equal_to(@b))
end
def test_extra
@a << 5
assert(!@a.equal_to(@b))
end
def test_subset_of_same_size
@a.pop
@a << 1
assert(!@a.equal_to(@b))
end
end
There’s an noteworthy lesson about testing here, by the way. My first
implementation of equal_to was:
def equal_to(other)
end
Interestingly, some of my tests passed – because the method returned
nil, and I was asserting (the truth of (not the method return value)).
It’s a useful reminder of the possibility of things working by
coincidence sometimes.
David
