Groups > comp.lang.javascript > #19952

Re: !0 versus true

Message-ID	<1639100.PjNAD8PV0k@PointedEars.de> (permalink)
From	Thomas 'PointedEars' Lahn <PointedEars@web.de>
Organization	PointedEars Software (PES)
Date	2013-05-25 07:00 +0200
Subject	Re: !0 versus true
Newsgroups	comp.lang.javascript
References	<gMWdnU1mmO68hwPMnZ2dnUVZ_sqdnZ2d@westnet.com.au> <4493946.nSsM8AgQI3@PointedEars.de> <a1Pnt.5879$OS5.4813@newsfe24.iad> <knooc3$qpi$1@dont-email.me>

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Denis McMahon wrote:

> On Fri, 24 May 2013 12:17:28 -0700, Daniel Pitts wrote:
>> Yes, but if (x === true) can not be reduced to if (x).
> 
> How about if(x===!0)

I think that was the point of the comment.  However, it is not a good idea.  
This is not just an equivalent expression.  Since we must not assume 
optimization, it includes an *additional operation* *each* time this 
statement is executed.  For what?  Two octets less loaded the *one* time it 
is loaded – a time savings of 0.3 ms in the *worst* case (56k dial-up 
modem)?

<http://samizdat.mines.edu/howto/HowToBeAProgrammer.html#id2789469>

> if "!0" is identical to "true" then the test "x===true" is identical to
> the test "x===!0"

And +!1 is equivalent to 0.  We still write only 0; not because it is 
shorter, but because it is *less complex*, i.e. *faster*.

> Where I use "is identical to" in the sense of "===", whereas I would use
> "is equivalent to" in the sense of "=="

Making up your private terminology is not helpful.  An *expression* is 
/equivalent/ to another *expression* if both expressions are evaluated to 
the same value under the same conditions; one expression can be exchanged 
with the other without affecting the outcome of expressions in which they 
are used.  A *value* is /identical/ to another *value* if both values are 
the same.

-- 
PointedEars

Twitter: @PointedEars2
Please do not Cc: me. / Bitte keine Kopien per E-Mail.

Thread

!0 versus true Andrew Poulos <ap_prog@hotmail.com> - 2013-05-23 23:31 +1000
  Re: !0 versus true Scott Sauyet <scott.sauyet@gmail.com> - 2013-05-23 07:58 -0700
  Re: !0 versus true Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2013-05-23 17:53 +0200
    Re: !0 versus true Daniel Pitts <newsgroup.nospam@virtualinfinity.net> - 2013-05-24 12:17 -0700
      Re: !0 versus true Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2013-05-24 21:56 +0200
        Re: !0 versus true Daniel Pitts <newsgroup.nospam@virtualinfinity.net> - 2013-05-24 13:13 -0700
          Re: !0 versus true Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2013-05-24 22:23 +0200
      Re: !0 versus true Denis McMahon <denismfmcmahon@gmail.com> - 2013-05-24 22:08 +0000
        Re: !0 versus true Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2013-05-25 07:00 +0200
          Re: !0 versus true Scott Sauyet <scott.sauyet@gmail.com> - 2013-05-25 20:04 -0700
            Re: !0 versus true "Evertjan." <exxjxw.hannivoort@inter.nl.net> - 2013-05-26 11:07 +0200
            Re: !0 versus true Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2013-05-26 13:11 +0200
              Re: !0 versus true Scott Sauyet <scott.sauyet@gmail.com> - 2013-05-26 13:28 -0700
                Re: !0 versus true Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2013-05-27 12:07 +0200
                Re: !0 versus true Scott Sauyet <scott.sauyet@gmail.com> - 2013-05-27 11:27 -0700
                Re: !0 versus true Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2013-05-27 23:30 +0200
                Re: !0 versus true Scott Sauyet <scott.sauyet@gmail.com> - 2013-05-27 17:12 -0700
                Re: !0 versus true Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2013-05-28 02:40 +0200
                Re: !0 versus true Scott Sauyet <scott.sauyet@gmail.com> - 2013-05-27 20:29 -0700
                Re: !0 versus true John Harris <niam@jghnorth.org.uk.invalid> - 2013-05-28 15:38 +0100
                Re: !0 versus true Scott Sauyet <scott.sauyet@gmail.com> - 2013-05-28 08:32 -0700
                Re: !0 versus true Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2013-05-28 21:14 +0200
                Re: !0 versus true Scott Sauyet <scott.sauyet@gmail.com> - 2013-05-28 15:38 -0700
                Re: !0 versus true Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2013-05-29 13:20 +0200
                Re: !0 versus true Scott Sauyet <scott.sauyet@gmail.com> - 2013-05-29 06:37 -0700
                Re: !0 versus true Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2013-05-29 16:28 +0200
                Re: !0 versus true Scott Sauyet <scott.sauyet@gmail.com> - 2013-05-29 13:32 -0700
                Re: !0 versus true Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2013-05-29 23:34 +0200
                Re: !0 versus true Scott Sauyet <scott.sauyet@gmail.com> - 2013-05-30 06:30 -0700
                Re: !0 versus true John Harris <niam@jghnorth.org.uk.invalid> - 2013-05-29 17:33 +0100
                Re: !0 versus true Scott Sauyet <scott.sauyet@gmail.com> - 2013-05-29 11:34 -0700
                Re: !0 versus true John Harris <niam@jghnorth.org.uk.invalid> - 2013-05-31 10:22 +0100
                Re: !0 versus true Christoph Becker <cmbecker69@gmx.de> - 2013-05-31 13:04 +0200
                Re: !0 versus true Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2013-05-31 18:13 +0200
                Re: !0 versus true Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2013-05-31 18:16 +0200
                Re: !0 versus true Scott Sauyet <scott.sauyet@gmail.com> - 2013-05-31 07:25 -0700
  Re: !0 versus true imma harper <immaterial_uk@yahoo.co.uk> - 2013-05-31 09:46 -0700
    Re: !0 versus true Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2013-05-31 21:38 +0200
    Re: !0 versus true John Harris <niam@jghnorth.org.uk.invalid> - 2013-06-01 17:37 +0100
  Re: !0 versus true Dr J R Stockton <reply1300@merlyn.demon.co.uk.invalid> - 2013-06-02 21:03 +0100
    Re: !0 versus true Scott Sauyet <scott.sauyet@gmail.com> - 2013-06-03 04:45 -0700
      Re: !0 versus true Dr J R Stockton <reply1300@merlyn.demon.co.uk.invalid> - 2013-06-04 17:23 +0100

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