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Re: How would you prepare for javascripting interview?

From Scott Sauyet <scott@sauyet.com>
Newsgroups comp.lang.javascript
Subject Re: How would you prepare for javascripting interview?
Date 2016-09-07 01:36 +0000
Organization A noiseless patient Spider
Message-ID <nqnqu2$a4v$1@dont-email.me> (permalink)
References (7 earlier) <nqf8t7$h37$1@dont-email.me> <nqhg6o$st6$1@dont-email.me> <nqkl2e$6bt$1@dont-email.me> <nqmpag$kit$1@dont-email.me> <9cstsb1uddjiltlflrdiks2ha2u3msi1ao@4ax.com>

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Gene Wirchenko wrote:
>> Scott Sauyet wrote:

>>> I disagree.  The realistic choices are
>>> 
>>>   (A) Return something of the correct type, even though it's not
>>>       in the (empty) input list.
>>> 
>>>   (B) Return some semaphore of a different type that signals that
>>>       things have gone wrong: `undefined` or `null` are most likely.
>>> 
>>>   (C) Throw an error.
>>> 
>>> None of these choices is ideal, but we have to choose between them. 
>>> I'd say that the best ordering is A > C > B.
> 
>      Depending on language, I would go with either B or C with both of
> them >> A.  A is horrible.  It gives the opportunity to proceed with
> garbage. [ ... ]

I probably shouldn't have used "garbage in, garbage out" earlier.  This 
is really not a case of that.

Stefan Ram was trying to explain this earlier in the thread.  I think 
it's easiest to argue this through some analogies:  A function such as 
`all` is straightforward:

    // all :: (a -> Bool) -> [a] -> Bool
    const all = (predicate, list) => list.reduce(
        (current, val) => current && predicate(val), 
        true
    );
    // all(n => n > 3, [8, 6, 7, 5]); //=> true
    // all(n => n > 3, [8, 6, 7, 5, 3, 0, 9]); //=> false

Note that 

    // all([]); //=> true

This is proper.  (If there's any doubt, read up on vacuous truths [1].)

But of course in this case, there is no entry, `val`, in the list for 
which `predicate(val)` returns true.  Although some people who don't 
understand vacuous truths are confused by this, generally this is easily 
accepted.  It's not only convenient, it's quite important, because it 
allows `all` to follow some useful laws, such as:

    all(p, list1) && all(p, list2) === all(p, concat(list1, list2))

We could also discuss the additive identity of 0 or multiplicative 
identity of 1, which have similar laws:

    sum(list1) + sum(list2) === sum(concat(list1, list2))
    product(list1) * product(list2) === product(concat(list1, list2))

These hold for any lists of numbers, even empty ones because 

    sum([]); //=> 0
    product([]); //=> 1

Of course we need suitable definitions of `concat`, `sum`, and `product` 
here, but it should be clear enough what those would entail.

So is there a reasonable equivalent law for `max`?  I say yes:

    max([max(list1), max(list2)]) === max(concat(list1, list2))

To make this true, `max([])` *must* be no greater than every valid 
number.  Javascript offers only one such value, `-Infinity`.

This is not simply an implementation convenience.  It goes to the heart 
of how the function is considered.  If we try to define it in some hand-
waving manner that implies that the result of `max` is specifically one 
of the inputs in the list, then we end up with a function less useful 
than it could be.


  [1]: <https://en.wikipedia.org/wiki/Vacuous_truth>

  -- Scott

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Thread

How would you prepare for javascripting interview? justaguy <lichunshen84@gmail.com> - 2016-07-18 09:10 -0700
  Re: How would you prepare for javascripting interview? Hans-Georg Michna <hans-georgNoEmailPlease@michna.com> - 2016-07-18 18:37 +0200
    Re: How would you prepare for javascripting interview? justaguy <lichunshen84@gmail.com> - 2016-07-18 11:09 -0700
      Re: How would you prepare for javascripting interview? Scott Sauyet <scott@sauyet.com> - 2016-07-21 01:04 +0000
        Re: How would you prepare for javascripting interview? John Harris <niam@jghnorth.org.uk.invalid> - 2016-07-21 14:24 +0100
        Re: How would you prepare for javascripting interview? Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2016-07-23 16:25 +0200
          Re: How would you prepare for javascripting interview? Doc O'Leary  <droleary@2015usenet1.subsume.com> - 2016-07-23 15:56 +0000
            Re: How would you prepare for javascripting interview? Scott Sauyet <scott@sauyet.com> - 2016-09-03 19:39 +0000
              Re: How would you prepare for javascripting interview? Doc O'Leary  <droleary@2015usenet1.subsume.com> - 2016-09-04 15:56 +0000
                Re: How would you prepare for javascripting interview? Ben Bacarisse <ben.usenet@bsb.me.uk> - 2016-09-05 00:06 +0100
                Re: How would you prepare for javascripting interview? John Harris <niam@jghnorth.org.uk.invalid> - 2016-09-05 14:49 +0100
                Re: How would you prepare for javascripting interview? $Bill <news@todbe.com> - 2016-09-05 10:01 -0700
                Re: How would you prepare for javascripting interview? Gene Wirchenko <genew@telus.net> - 2016-09-06 09:36 -0700
                Re: How would you prepare for javascripting interview? John Harris <niam@jghnorth.org.uk.invalid> - 2016-09-05 15:05 +0100
                Re: How would you prepare for javascripting interview? Andreas Bergmaier <andber93@web.de> - 2016-09-05 20:31 +0200
                Re: How would you prepare for javascripting interview? Doc O'Leary  <droleary@2015usenet1.subsume.com> - 2016-09-06 15:15 +0000
                Re: How would you prepare for javascripting interview? Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2016-09-06 19:40 +0200
                Re: How would you prepare for javascripting interview? John Harris <niam@jghnorth.org.uk.invalid> - 2016-09-06 19:25 +0100
                Re: How would you prepare for javascripting interview? Andreas Bergmaier <andber93@web.de> - 2016-09-06 22:16 +0200
                Re: How would you prepare for javascripting interview? John Harris <niam@jghnorth.org.uk.invalid> - 2016-09-07 17:17 +0100
                Re: How would you prepare for javascripting interview? Andreas Bergmaier <andber93@web.de> - 2016-09-07 20:07 +0200
                Re: How would you prepare for javascripting interview? John Harris <niam@jghnorth.org.uk.invalid> - 2016-09-08 14:36 +0100
                Re: How would you prepare for javascripting interview? Scott Sauyet <scott@sauyet.com> - 2016-09-05 18:46 +0000
                Re: How would you prepare for javascripting interview? Ben Bacarisse <ben.usenet@bsb.me.uk> - 2016-09-05 20:32 +0100
                Re: How would you prepare for javascripting interview? Doc O'Leary  <droleary@2015usenet1.subsume.com> - 2016-09-05 17:27 +0000
                Re: How would you prepare for javascripting interview? Ben Bacarisse <ben.usenet@bsb.me.uk> - 2016-09-05 20:12 +0100
                Re: How would you prepare for javascripting interview? Doc O'Leary  <droleary@2015usenet1.subsume.com> - 2016-09-06 16:48 +0000
                Re: How would you prepare for javascripting interview? Andreas Bergmaier <andber93@web.de> - 2016-09-06 19:56 +0200
                Re: How would you prepare for javascripting interview? Doc O'Leary  <droleary@2015usenet1.subsume.com> - 2016-09-07 20:16 +0000
                Re: How would you prepare for javascripting interview? Gene Wirchenko <genew@telus.net> - 2016-09-07 10:01 -0700
                Re: How would you prepare for javascripting interview? Doc O'Leary  <droleary@2015usenet1.subsume.com> - 2016-09-07 20:21 +0000
                Re: How would you prepare for javascripting interview? Gene Wirchenko <genew@telus.net> - 2016-09-09 11:41 -0700
                Re: How would you prepare for javascripting interview? "Michael Haufe (TNO)" <tno@thenewobjective.com> - 2016-09-09 15:35 -0700
                Re: How would you prepare for javascripting interview? "Michael Haufe (TNO)" <tno@thenewobjective.com> - 2016-09-09 20:40 -0700
                Re: How would you prepare for javascripting interview? Doc O'Leary  <droleary@2015usenet1.subsume.com> - 2016-09-10 15:12 +0000
                Re: How would you prepare for javascripting interview? Gene Wirchenko <genew@telus.net> - 2016-09-12 11:14 -0700
                Re: How would you prepare for javascripting interview? Doc O'Leary  <droleary@2015usenet1.subsume.com> - 2016-09-13 21:07 +0000
                Re: How would you prepare for javascripting interview? Doc O'Leary  <droleary@2015usenet1.subsume.com> - 2016-09-06 16:20 +0000
                Re: How would you prepare for javascripting interview? Ken Tilton <kentilton@gmail.com> - 2016-09-05 11:37 -0700
                Re: How would you prepare for javascripting interview? Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2016-09-06 19:26 +0200
                Re: How would you prepare for javascripting interview? "Michael Haufe (TNO)" <tno@thenewobjective.com> - 2016-09-08 12:41 -0700
                Re: How would you prepare for javascripting interview? Scott Sauyet <scott@sauyet.com> - 2016-09-05 20:37 +0000
                Re: How would you prepare for javascripting interview? Ben Bacarisse <ben.usenet@bsb.me.uk> - 2016-09-05 22:13 +0100
                Re: How would you prepare for javascripting interview? Scott Sauyet <scott@sauyet.com> - 2016-09-06 02:33 +0000
                Re: How would you prepare for javascripting interview? Doc O'Leary  <droleary@2015usenet1.subsume.com> - 2016-09-06 16:02 +0000
                Re: How would you prepare for javascripting interview? Gene Wirchenko <genew@telus.net> - 2016-09-06 09:50 -0700
                Re: How would you prepare for javascripting interview? Scott Sauyet <scott@sauyet.com> - 2016-09-07 01:36 +0000
                Re: How would you prepare for javascripting interview? Gene Wirchenko <genew@telus.net> - 2016-09-07 10:07 -0700
                Re: How would you prepare for javascripting interview? Scott Sauyet <scott@sauyet.com> - 2016-09-10 00:03 +0000
                Re: How would you prepare for javascripting interview? Scott Sauyet <scott@sauyet.com> - 2016-09-10 00:12 +0000
                Re: How would you prepare for javascripting interview? Doc O'Leary  <droleary@2015usenet1.subsume.com> - 2016-09-10 15:34 +0000
                Re: How would you prepare for javascripting interview? Ben Bacarisse <ben.usenet@bsb.me.uk> - 2016-09-11 01:32 +0100
                Re: How would you prepare for javascripting interview? Doc O'Leary  <droleary@2015usenet1.subsume.com> - 2016-09-12 19:26 +0000
                Re: How would you prepare for javascripting interview? Ben Bacarisse <ben.usenet@bsb.me.uk> - 2016-09-13 01:02 +0100
                Re: How would you prepare for javascripting interview? Doc O'Leary  <droleary@2015usenet1.subsume.com> - 2016-09-13 21:38 +0000
                Re: How would you prepare for javascripting interview? "Christoph M. Becker" <cmbecker69@arcor.de> - 2016-09-14 00:56 +0200
                Re: How would you prepare for javascripting interview? Doc O'Leary  <droleary@2015usenet1.subsume.com> - 2016-09-15 15:09 +0000
                Re: How would you prepare for javascripting interview? Ben Bacarisse <ben.usenet@bsb.me.uk> - 2016-09-14 00:47 +0100
                Re: How would you prepare for javascripting interview? Doc O'Leary  <droleary@2015usenet1.subsume.com> - 2016-09-15 15:34 +0000
                Re: How would you prepare for javascripting interview? Scott Sauyet <scott@sauyet.com> - 2016-09-11 02:45 +0000
                Re: How would you prepare for javascripting interview? Doc O'Leary  <droleary@2015usenet1.subsume.com> - 2016-09-12 19:10 +0000
                Re: How would you prepare for javascripting interview? Ben Bacarisse <ben.usenet@bsb.me.uk> - 2016-09-12 21:06 +0100
                Re: How would you prepare for javascripting interview? Scott Sauyet <scott@sauyet.com> - 2016-09-07 03:12 +0000
                Re: How would you prepare for javascripting interview? Doc O'Leary  <droleary@2015usenet1.subsume.com> - 2016-09-07 19:53 +0000
                Re: How would you prepare for javascripting interview? Scott Sauyet <scott@sauyet.com> - 2016-09-10 02:14 +0000
                Re: How would you prepare for javascripting interview? John Harris <niam@jghnorth.org.uk.invalid> - 2016-09-10 11:25 +0100
                Re: How would you prepare for javascripting interview? Ben Bacarisse <ben.usenet@bsb.me.uk> - 2016-09-10 15:49 +0100
                Re: How would you prepare for javascripting interview? Doc O'Leary  <droleary@2015usenet1.subsume.com> - 2016-09-10 18:39 +0000
                Re: How would you prepare for javascripting interview? Scott Sauyet <scott@sauyet.com> - 2016-09-11 02:45 +0000
                Re: How would you prepare for javascripting interview? John Harris <niam@jghnorth.org.uk.invalid> - 2016-09-11 16:23 +0100
                Re: How would you prepare for javascripting interview? Ben Bacarisse <ben.usenet@bsb.me.uk> - 2016-09-12 20:32 +0100
                Re: How would you prepare for javascripting interview? Doc O'Leary  <droleary@2015usenet1.subsume.com> - 2016-09-12 18:49 +0000
                Re: How would you prepare for javascripting interview? Scott Sauyet <scott@sauyet.com> - 2016-09-13 00:27 +0000
                Re: How would you prepare for javascripting interview? Tim Streater <timstreater@greenbee.net> - 2016-09-13 08:51 +0100
                Re: How would you prepare for javascripting interview? Jon Ribbens <jon+usenet@unequivocal.eu> - 2016-09-13 12:33 +0000
                Re: How would you prepare for javascripting interview? Scott Sauyet <scott@sauyet.com> - 2016-09-14 01:17 +0000
                Re: How would you prepare for javascripting interview? Tim Streater <timstreater@greenbee.net> - 2016-09-14 11:15 +0100
                Re: How would you prepare for javascripting interview? Doc O'Leary  <droleary@2015usenet1.subsume.com> - 2016-09-15 15:02 +0000
                Re: How would you prepare for javascripting interview? John Harris <niam@jghnorth.org.uk.invalid> - 2016-09-13 10:06 +0100
                Re: How would you prepare for javascripting interview? John Harris <niam@jghnorth.org.uk.invalid> - 2016-09-06 19:53 +0100
    Re: How would you prepare for javascripting interview? Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2016-07-18 22:30 +0200
  Re: How would you prepare for javascripting interview? justaguy <lichunshen84@gmail.com> - 2016-07-18 14:56 -0700
  Re: How would you prepare for javascripting interview? Joao Rodrigues <groups_jr-1@yahoo.com.br> - 2016-07-19 16:01 -0300
    Re: How would you prepare for javascripting interview? Joao Rodrigues <groups_jr-1@yahoo.com.br> - 2016-07-19 16:16 -0300

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