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Re: bitwise vs. logical OR operator (was: ISO 8601 Code Review Wanted)

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On Friday, May 16, 2014 3:50:15 AM UTC-7, Christoph Michael Becker wrote:
> Evertjan. wrote:
> 
> 
> 
> > Christoph Michael Becker <cmbecker69@arcor.de> wrote on 16 mei 2014 in 
> 
> > comp.lang.javascript:
> 
> > 
> 
> >> Evertjan. wrote:
> 
> >>
> 
> >>> Christoph Michael Becker <cmbecker69@arcor.de> wrote on 15 mei 2014 in 
> 
> >>> comp.lang.javascript:
> 
> >>>
> 
> >>>> Furthermore there seems to be a bug at the end of setTime, where you're
> 
> >>>> using a | operator instead of || for the default of ss.
> 
> >>>
> 
> >>> alert(12|0) // 12
> 
> >>> alert(12|1) // 13 !
> 
> >>> alert(13|1) // 13
> 
> >>> alert('13'|1) // 13
> 
> >>> alert('13'|0) // 13
> 
> >>> alert('13x'|0) // 0 !
> 
> >>>
> 
> >>> alert(12||0) // 12
> 
> >>> alert(12||1) // 12 !
> 
> >>> alert(13||1) // 13
> 
> >>> alert('13'||1) // 13
> 
> >>> alert('13'||0) // 13
> 
> >>> alert('13x'||0) // 13x !
> 
> >>>
> 
> >>> methinks ss|0 is slightly better,
> 
> >>> as it zeros inconvertable strings.
> 
> >>
> 
> >> No, at least not in this case.
> 
> > 
> 
> > I was not talking about this special case.
> 
> 
> 
> Okay.  It wasn't clear to me because you had not changed the subject
> 
> line, and have been quoting the issue in the OP's code that I mentioned.
> 
> 
> 
> >> ss is either a string with exactly two
> 
> >> decimal digits or undefined (see the OP's full code[1]).  
> 
> > 
> 
> > In general one would consider all cases.
> 
> 
> 
> Not necessarily.  It depends on what one wants to achieve.
> 
> 
> 
> >> As you already
> 
> >> have examined, using the binary bitwise OR operator can lead to false
> 
> >> results, 
> 
> > 
> 
> > Not in the case of x|0, as it does not change any numeric x,
> 
> > and zeros all other x values. 
> 
> 
> 
> My bad.  Of course you're right wrt. to values that can be represented
> 
> as 32 bit integers.
> 
> 

Right.

var x = Math.pow(2, 31);
x; // 2147483648
x|0; // -2147483648


> 
> > Now x||0 does not do that in the case that x is a string.
> 
> > 
> 
> >> while the binary logical OR operator is exactly what is
> 
> >> desired: use zero as default, when ss is falsy.
> 
> > 
> 
> > This NG is about javascript, I wish to discuss general cases.
> 
> 
> 
> However, whether the bitwise or the logical OR operator is correct (or
> 
> better suited) depends on the requirements.  These requirements have to
> 
> be stated, before a solution can be discussed.  It is not clear to me
> 
> which requirements you have in mind when suggesting using |0.
> 
> Converting a numeric argument to a number can also be done with
> 
> 
> 
>   +x
> 
> 
That's a different conversion. Unary plus is ToNumber. Bitwise OR is ToInt32. 

var x = undefined;
+x === 0; // false
(x|0) === 0; // true

It worked in that case because `ss` was undefined. But it was actually a typo.



> 
> >> Using the binary logical operator for this purpose is a common ES idiom,
> 

I agree.  s||0 was what I wanted. I had a typo and it actually worked.

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Thread

ISO 8601 Code Review Wanted garrett.smith@acxiom.com - 2014-05-14 09:59 -0700
  Re: ISO 8601 Code Review Wanted John Harris <niam@jghnorth.org.uk.invalid> - 2014-05-15 10:15 +0100
    Re: ISO 8601 Code Review Wanted Christoph Michael Becker <cmbecker69@arcor.de> - 2014-05-15 21:31 +0200
      Re: ISO 8601 Code Review Wanted dhtml <dhtmlkitchen@gmail.com> - 2014-05-15 12:53 -0700
        Re: ISO 8601 Code Review Wanted dhtml <dhtmlkitchen@gmail.com> - 2014-05-15 13:12 -0700
        Re: ISO 8601 Code Review Wanted Christoph Michael Becker <cmbecker69@arcor.de> - 2014-05-15 22:21 +0200
          Re: ISO 8601 Code Review Wanted "Evertjan." <exxjxw.hannivoort@inter.nl.net> - 2014-05-16 00:44 +0200
            Re: ISO 8601 Code Review Wanted Christoph Michael Becker <cmbecker69@arcor.de> - 2014-05-16 01:26 +0200
              Re: ISO 8601 Code Review Wanted "Evertjan." <exxjxw.hannivoort@inter.nl.net> - 2014-05-16 09:39 +0200
                bitwise vs. logical OR operator (was: ISO 8601 Code Review Wanted) Christoph Michael Becker <cmbecker69@arcor.de> - 2014-05-16 12:50 +0200
                Re: bitwise vs. logical OR operator (was: ISO 8601 Code Review Wanted) dhtml <dhtmlkitchen@gmail.com> - 2014-05-16 11:21 -0700
  Re: ISO 8601 Code Review Wanted Dr J R Stockton <reply1400@merlyn.demon.co.uk.invalid> - 2014-05-16 22:26 +0100
    Re: ISO 8601 Code Review Wanted dhtml <dhtmlkitchen@gmail.com> - 2014-05-19 11:56 -0700
      Re: ISO 8601 Code Review Wanted dhtml <dhtmlkitchen@gmail.com> - 2014-05-19 17:03 -0700
        Re: ISO 8601 Code Review Wanted Dr J R Stockton <reply1400@merlyn.demon.co.uk.invalid> - 2014-05-21 17:30 +0100
          Re: ISO 8601 Code Review Wanted John Harris <niam@jghnorth.org.uk.invalid> - 2014-05-22 10:20 +0100
            Re: ISO 8601 Code Review Wanted Dr J R Stockton <reply1400@merlyn.demon.co.uk.invalid> - 2014-05-23 20:44 +0100
              Re: ISO 8601 Code Review Wanted John Harris <niam@jghnorth.org.uk.invalid> - 2014-05-24 15:54 +0100
          Re: ISO 8601 Code Review Wanted Tim Streater <timstreater@greenbee.net> - 2014-05-22 18:46 +0100
            Re: ISO 8601 Code Review Wanted dhtml <dhtmlkitchen@gmail.com> - 2014-05-25 22:18 -0700
              Re: ISO 8601 Code Review Wanted Tim Streater <timstreater@greenbee.net> - 2014-05-26 11:41 +0100
                Re: ISO 8601 Code Review Wanted dhtml <dhtmlkitchen@gmail.com> - 2014-05-28 09:54 -0700
          Re: ISO 8601 Code Review Wanted dhtml <dhtmlkitchen@gmail.com> - 2014-05-23 10:37 -0700
            Re: ISO 8601 Code Review Wanted Dr J R Stockton <reply1400@merlyn.demon.co.uk.invalid> - 2014-05-24 19:09 +0100
  Re: ISO 8601 Code Review Wanted dhtml <dhtmlkitchen@gmail.com> - 2014-05-23 13:14 -0700

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