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From: John Smith on 25 Feb 2010 11:12
Question about an array. Say I have the following array...

textlist = ["Apple", "Orange", "Lemon", "Grape", "Orange", "Melon",
"Orange", "Banana"]

if I did textlist.index("Orage"), I would get "1" returned.

Can anyone tell me how I could retrieve the index number of the 2nd
instance of "Orange"?

Thanks in advance!
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From: Rob Biedenharn on 25 Feb 2010 12:15
On Feb 25, 2010, at 11:12 AM, John Smith wrote:
> Question about an array. Say I have the following array...
>
> textlist = ["Apple", "Orange", "Lemon", "Grape", "Orange", "Melon",
> "Orange", "Banana"]
>
> if I did textlist.index("Orage"), I would get "1" returned.
"Orage" #=> nil
"Orange" #=> 1 ;-)

>
> Can anyone tell me how I could retrieve the index number of the 2nd
> instance of "Orange"?
>
> Thanks in advance!

Well, I thought this was a simple answer, but I was remembering
String#index(string, offset)

something like this:

def textlist.where_is(target)
locations = []
each_with_index {|e,i| locations << i if target === e }
return nil if locations.empty?
locations
end

textlist.where_is("Orange") #=> [1,4,6]
textlist.where_is("Cherry") #=> nil
textlist.where_is("Grape") #=> [3]

Define it on Array if you want or in a module to extend any object you
want.

-Rob

Rob Biedenharn http://agileconsultingllc.com
Rob(a)AgileConsultingLLC.com




From: David Springer on 25 Feb 2010 13:20
Please excuse my newbieness, second day with Ruby.

textlist = ["Apple", "Orange", "Lemon", "Grape", "Orange",
"Melon","Orange", "Banana"]

i = textlist.index("Orange")

if !i.nil?
puts "textlist[" << i.to_s << "] is \"" << textlist[i] << "\""
j = textlist[i+1,textlist.length-i-1].index("Orange")+i+1
if !j.nil?
puts "textlist[" << j.to_s << "] is \"" << textlist[j] << "\""
end
end


outputs:


textlist[1] is "Orange"
textlist[4] is "Orange"
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From: Luc Heinrich on 25 Feb 2010 13:39
On 25 févr. 2010, at 19:20, David Springer wrote:

> textlist = ["Apple", "Orange", "Lemon", "Grape", "Orange",
> "Melon","Orange", "Banana"]
>
> i = textlist.index("Orange")
>
> if !i.nil?
> puts "textlist[" << i.to_s << "] is \"" << textlist[i] << "\""
> j = textlist[i+1,textlist.length-i-1].index("Orange")+i+1
> if !j.nil?
> puts "textlist[" << j.to_s << "] is \"" << textlist[j] << "\""
> end
> end

class Array
def indexes_of(obj)
indexes = Array.new
self.each_with_index {|s,i| indexes << i if s === obj }
return indexes
end
end

textlist = ["Apple", "Orange", "Lemon", "Grape", "Orange", "Melon","Orange", "Banana"]
p textlist.indexes_of("Orange")

#=> [1,4,6]

--
Luc Heinrich - luc(a)honk-honk.com


From: David Springer on 25 Feb 2010 17:13
after some inspiration from Luc I was able to come up with this:

textlist = ["Apple", "Orange", "Lemon", "Grape", "Orange",

(0..textlist.length-1).select {|i| textlist[i] == "Orange"}[1]



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