Sorting arrays

Ruby
21

Hi –

On Mon, 10 Jul 2006, Dark A. wrote:

is true.
if lowest == nil || item < lowest <----then expression 1 is true (as you
say above).

Correct. Therefore this gets executed:

lowest = item

So now, lowest is item – which was “five” (or whatever the first
array item was).

So next time through the loop, this:

lowest == nil

will not be true. So this:

item < lowest

will be tested instead.

David

22

David,

Thank you for your patience. I now get it! As you mentioned previously
the first time through your loop, lowest is nil – which means that the
item < lowest comparison is never evaluated, second iteration (via
lowest =
item) changes it.
Why I didn’t see it then.

Apologies
Stuart

23

On 7/9/06, [email protected] [email protected] wrote:

I don’t see that in your code. I see this:

lowest = nil

So this:

lowest == nil

is true.

Sorry I’m not trying to be frustrating.

def sort(list)
sorted = []
unsorted = []

lowest = nil <----------- here lowest is being set to nil
list.each do |item|
if lowest == nil || item < lowest <----then expression 1 is true (as
you
say above).

lowest = item
end
end

I might just be missing a brain, because it seems like it’s not sinking
through.

Stuart

24

I’m back already :). Basically I’m trying to take James original
recursion
version and do it with recursion. Anyway, my questions are below in the
<---------------- lines.
TIA
Stuart

def sort(list)
sorted = []
unsorted = []
puts 'here is list: ’
puts list <------ Here i’m outputing the list I put in to the method

prints out the entire list
puts

lowest = nil
list.each do |item|
if lowest == nil || item < lowest

  lowest = item
end

end
sorted.push(lowest)

make a new unsorted list, minus the low guy

unsorted = [ ]
added = false
list.each do |item|
if added == false and item == lowest
added = true
else
unsorted.push(item)
end
end

puts ‘Here is the unsorted list’
puts unsorted
puts
puts ‘Here is the sorted list’
puts sorted
puts
puts ‘Here is list’ <----------------------- Here though, the list
is
empty (at least of values). Something I don’t get, since I didn’t see
any
.delete
puts
puts 'list size is: '<---------------------------yet here the size
returned is 5 the number of original elements.
puts list.size

third step (from James’ is where he returns control to method (or

back
to recursion)
#if list.size == 0

sorted

#else

recursive_sort(unsorted, sorted)

#end
end #end of method

mylist = [‘ten’, ‘eight’, ‘one’, ‘six’, ‘five’]

sort mylist