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Re: How to check if the n-th part of an array of Strings exist?

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Eric Sosman writes:
> On 10/27/2011 9:45 AM, Mayeul wrote:
> > On 27/10/2011 15:09, Tim Slattery wrote:
> >> Eric Sosman wrote:
> >>
> >>> On 10/27/2011 3:20 AM, Jussi Piitulainen wrote:
> >>>> Shame that (0<= index< part.length) means something useless instead.
> >>>
> >>> Be thankful that its meaning in Java is more useful than in C.
> >>
> >> Please explain that. I'm probably wrong, but I'd think they'd be the
> >> same.
> >>
> >> Evaluate one of the comparisons (not positive which one), resulting in
> >> a boolean. Convert the boolean to a number to do the other comparison.
> >> Not very useful.
> >
> > I'd wager that refusing to compile is more useful than meaning something
> > useless and confusing, therefore errors-prone.
> 
>      Bingo.  (That at least is what I meant; whether it's "true" is
> another matter entirely.)
> 
>      In C, `x < y < z' has a well-defined meaning, but one that is so
> very unlikely to be intended that it is almost surely a mistake.  The
...
>      In Java `x < y < z' is a compile-time error.
> 
>      That's why I think Java's interpretation is superior.  Not that
> Java gets *everything* right: If x,y,z are booleans `x == y == z'
> is valid and means something other than what might be expected.
> Still, it's an improvement on C.

Java does not get this right. It's merely a mild improvement on C.
Python gets this right: 0 <= k < n means what one expects.

Comparison chains are not hard to understand or implement: just add a
syntactic category of relation symbols (<, >, <=, >=, ==, !=) with the
same low precedence, associative, and give the resulting expression
the intended meaning that everybody learns to expect in school.

Since the current meaning of chained comparisons in Java is not useful
for much anything, the change would not be impossible. This does not
mean that I expect it to happen. I do not expect it to happen.

The languages that get chained comparisons right have some bragging
rights over Lisp. While Lisp does 0 < k < n with ease, it gets uneasy
with the different comparisons in 0 <= k < n, which often is what one
wants to test.

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How to check if the n-th part of an array of Strings exist? jochen2@brenz.com (Jochen Brenzlinger) - 2011-10-25 16:26 +0000
  Re: How to check if the n-th part of an array of Strings exist? Tom McGlynn <taqmcg@gmail.com> - 2011-10-25 09:41 -0700
  Re: How to check if the n-th part of an array of Strings exist? Wojtek <nowhere@a.com> - 2011-10-26 23:37 -0700
    Re: How to check if the n-th part of an array of Strings exist? Jussi Piitulainen <jpiitula@ling.helsinki.fi> - 2011-10-27 10:20 +0300
      Re: How to check if the n-th part of an array of Strings exist? Eric Sosman <esosman@ieee-dot-org.invalid> - 2011-10-27 07:26 -0400
        Re: How to check if the n-th part of an array of Strings exist? Tim Slattery <Slattery_T@bls.gov> - 2011-10-27 09:09 -0400
          Re: How to check if the n-th part of an array of Strings exist? Mayeul <mayeul.marguet@free.fr> - 2011-10-27 15:45 +0200
            Re: How to check if the n-th part of an array of Strings exist? Jussi Piitulainen <jpiitula@ling.helsinki.fi> - 2011-10-27 16:55 +0300
            Re: How to check if the n-th part of an array of Strings exist? Gene Wirchenko <genew@ocis.net> - 2011-10-27 10:37 -0700
              Re: How to check if the n-th part of an array of Strings exist? Tassilo Horn <tassilo@member.fsf.org> - 2011-10-27 21:31 +0200
            Re: How to check if the n-th part of an array of Strings exist? Eric Sosman <esosman@ieee-dot-org.invalid> - 2011-10-27 21:25 -0400
              Re: How to check if the n-th part of an array of Strings exist? Jussi Piitulainen <jpiitula@ling.helsinki.fi> - 2011-10-28 10:08 +0300
  Re: How to check if the n-th part of an array of Strings exist? Roedy Green <see_website@mindprod.com.invalid> - 2011-10-28 06:20 -0700
  Re: How to check if the n-th part of an array of Strings exist? Arne Vajhøj <arne@vajhoej.dk> - 2011-11-06 14:54 -0500

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