From: John W Higgins <wishdev@...>
Date: 2010-12-28T03:10:53+09:00
Subject: Re: inject issue

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Good Morning,

On Mon, Dec 27, 2010 at 9:25 AM, jzakiya <jzakiya@gmail.com> wrote:

> I was wondering why these are equivalent:
>
> a=(1..100).inject :+
> b=(1..100).inject 0, :+
>
> Those are equivalent by luck only. With inject if you fail to provide the
initial "value" (as you do in the first line) then the first element of the
collection is used (in the first line it would be 1).

So, for example if you used :* or :- instead of :+ for your two rows you
would see a different result for the two rows - using :* would return a very
large number for the first row and zero for the second row (the second row
would just keep multiplying numbers by 0 which always equals 0). For :- you
would have something like -5049 and the second row would be -5050 (or
something close to that).

In the example you provided your second row uses 0 as the initial value
which means after processing the first element of the collection you are in
the same position as not having provided the value, as the first row does,
because 1 = 0 + 1.

John

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