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Re: How to parse an array?

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On 25.06.2017 00:42, Martin Gregorie wrote:
> On Sat, 24 Jun 2017 16:34:08 -0400, Jerry Stuckle wrote:
> 
>> On 6/20/2017 3:29 PM, Stefan Ram wrote:
>>> Eric Douglas <e.d.programmer@gmail.com> writes:
>>>> I'm writing a method to take 2 arrays and return the subset of the
>>>> first array.
>>>
>>>    »The subset of the first array« makes no sense in English,
>>>    because
>>>
>>>
>> It makes perfect sense in the mathematical realm.  A set is a group of
>> values (or similar).  A subset is another group of values, all of which
>> are members of the original set.  The subset may contain all of the
>> values in the original set, or only some of the values in the original
>> set.  But it does not contain any values not in the original set.
>>
> However, this doesn't apply to the OP's example code. His larger array
> contains alphabetic valueds, while the second list contains integer
> values, IOW it is not a subset of the first array.

No, but the result is.

>> In this particular case, a subset of the array would be another array
>> containing some (or all) of the values in the original array.
>>
> But that's not what it contains.

I am with Jerry here: the result ("retval") does indeed contain a subset 
of the entries in "list1", because it does contain some values from it.

> In fact it looks as though its meant to  be a list of subscripts
> referencing the first array. I don't know what I'd call it other than a
> list of subscripts, but it clearly doesn't match your definition of a
> subset.

Yes, "list2" is a list of subscripts or indexes.  But Eric never talked 
about that as a subset.  He wants to _return_ a "subset of the first 
array" (see above) - "list1" and "list2" are obviously the inputs.

You may claim that Eric's wording is imprecise (e.g. he does not explain 
the role of sorting the result) and a lot of context is lacking which 
prevents us from fully assessing the fitness of his approach - but the 
problem does make sense and he specifically does not abuse the term 
"subset".

Kind regards

	robert

-- 
remember.guy do |as, often| as.you_can - without end
http://blog.rubybestpractices.com/

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Thread

How to parse an array? Eric Douglas <e.d.programmer@gmail.com> - 2017-06-20 12:18 -0700
  Re: How to parse an array? Knute Johnson <nospam@rabbitbrush.frazmtn.com> - 2017-06-20 14:49 -0500
  Re: How to parse an array? Arne Vajhøj <arne@vajhoej.dk> - 2017-06-20 16:15 -0400
  Re: How to parse an array? Eric Sosman <esosman@comcast-dot-net.invalid> - 2017-06-20 16:23 -0400
  Re: How to parse an array? Robert Klemme <shortcutter@googlemail.com> - 2017-06-24 12:02 +0200
    Re: How to parse an array? Eric Douglas <e.d.programmer@gmail.com> - 2017-06-26 05:10 -0700
      Re: How to parse an array? Eric Sosman <esosman@comcast-dot-net.invalid> - 2017-06-26 09:36 -0400
        Re: How to parse an array? Eric Douglas <e.d.programmer@gmail.com> - 2017-06-26 07:47 -0700
          Re: How to parse an array? Martin Gregorie <martin@address-in-sig.invalid> - 2017-06-26 15:47 +0000
        Re: How to parse an array? Arne Vajhøj <arne@vajhoej.dk> - 2017-06-26 20:37 -0400
      Re: How to parse an array? lewbloch@gmail.com - 2017-06-27 12:29 -0700
        Re: How to parse an array? Eric Douglas <e.d.programmer@gmail.com> - 2017-06-27 12:50 -0700
          Re: How to parse an array? Martin Gregorie <martin@address-in-sig.invalid> - 2017-06-27 20:05 +0000
            Re: How to parse an array? Eric Douglas <e.d.programmer@gmail.com> - 2017-06-27 14:01 -0700
              Re: How to parse an array? Martin Gregorie <martin@address-in-sig.invalid> - 2017-06-27 22:34 +0000
                Re: How to parse an array? Eric Douglas <e.d.programmer@gmail.com> - 2017-06-28 05:10 -0700
                Re: How to parse an array? Martin Gregorie <martin@address-in-sig.invalid> - 2017-06-28 19:09 +0000
                Re: How to parse an array? Eric Douglas <e.d.programmer@gmail.com> - 2017-06-28 13:02 -0700
                Re: How to parse an array? Martin Gregorie <martin@address-in-sig.invalid> - 2017-06-28 21:55 +0000
                Re: How to parse an array? Eric Douglas <e.d.programmer@gmail.com> - 2017-06-30 06:10 -0700
                Re: How to parse an array? Martin Gregorie <martin@address-in-sig.invalid> - 2017-06-30 16:52 +0000
  Re: How to parse an array? Jerry Stuckle <jstucklex@attglobal.net> - 2017-06-24 16:34 -0400
    Re: How to parse an array? Martin Gregorie <martin@address-in-sig.invalid> - 2017-06-24 22:42 +0000
      Re: How to parse an array? Jerry Stuckle <jstucklex@attglobal.net> - 2017-06-24 20:05 -0400
      Re: How to parse an array? Robert Klemme <shortcutter@googlemail.com> - 2017-06-25 12:20 +0200

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