From: Dave Aronson <rubytalk2dave@...>
Date: 2012-09-28T00:44:26+09:00
Subject: Re: subtract values of a array

On Thu, Sep 27, 2012 at 11:36 AM, Roelof Wobben <rwobben@hotmail.com> wrote:

> def subtract(*numbers)
>   numbers.inject(0) { |sum, number| sum - number }
> end
>
> but that won't work  subtract ( 4,5) gives -9  when -1 is the right answer.

You're overthinking it.  Look at a simpler usage of inject.

I find it useful to think of inject as injecting the operation between
each element of the array it's given, and if it's given an argument as
well (not an operation, one to treat as a starting value), then
between that and the start as well.  So what you've done there is tell
it to do, essentially, 0 - 4 - 5.  All you want is 4 - 5.  How would
you eliminate the "0 -" part?  Hint: the argument is optional.

-Dave

-- 
Dave Aronson, T. Rex of Codosaurus, LLC... aka
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