From: "David A. Black" <dblack@...>
Date: 2007-10-02T19:22:10+09:00
Subject: Re: a = b = c    order of evaluation weird

Hi --

On Tue, 2 Oct 2007, SpringFlowers AutumnMoon wrote:

> i thought if it is
>
>  a = b = c
>
> due to associativity rule, then it is
>
>  a = (b = c)
>
> so (b = c) is evaluated first.  and then now it will be a =
> (evaluated_value)
>
> now how come when
>
>  a = Array(1..100)
>
> and to cut off the first 1/3 and last 1/3 of the array to get about 33
> elements, shouldn't we use
>
>  a[0..a.size/2] = a[a.size*2/3..-1] = nil
>
> as after the last 1/3 is deleted, you got about 66 elements remaining
> and we want the other half deleted, to get to 33 elements.  However, it
> won't work and requires
>
>  a[0..a.size/3] = a[a.size*2/3..-1] = nil
>
> why is that?

Although the = associates to the right, the subscript expressions are
evaluated first. So you're really doing:

   a[0..50] = a[66..-1] = nil


David

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