From: dblack@...
Date: 2007-09-05T19:51:56+09:00
Subject: Re: assigning to hash keys when there is a default value?

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Hi --

On Wed, 5 Sep 2007, Pe=F1a, Botp wrote:

> From: Robert Klemme [mailto:shortcutter@googlemail.com]
> # 2007/9/4, Yossef Mendelssohn <ymendel@pobox.com>:
> # > If '"x+=3D1" will always be "x=3Dx+1"', what's the problem in
> # having x ||=3D
> # > 1 always be x =3D x || 1?
> # That an assignment of x=3Dx is useless (basically a nop in the standard
> # case of x being a variable).
>
> consider,
>
> irb(main):074:0* h=3DHash.new
> =3D> {}
> irb(main):075:0> h[5] =3D h[5]
> =3D> nil
> irb(main):076:0> h
> =3D> {5=3D>nil}
> irb(main):062:0* h=3DHash.new(1)
> =3D> {}
> irb(main):063:0> h[5] =3D h[5]
> =3D> 1
> irb(main):064:0> h
> =3D> {5=3D>1}
>
> thus h[k] =3D h[k] could mean
>    h[k] =3D h.default   or
>    h[k] =3D nil
>
> definitely not useless and not noop.

It's really always h[k] =3D h.default -- it's just that the default
default, so to speak, is nil.


David

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