in reply to Range check with unordered limits

Dear monks, thanks for your insights and extensions!

I did this one-liner as a fun task (because i was too lazy to detect min and max values beforehand) while working with integer values.

I agree with syphilis and LanX that

$inRange = (($a <=> $x) * ($b <=> $x)) <= 0;

is the most canonical form, where <= emphasizes the inclusion of the limits while < would hint for the exclusion.

My previous attempt was

$inRange = ($x > $a == $x < $b) || $x == $a || $x == $b; (inclusive)
$inRange = ($x > $a == $x < $b); (exclusive)

which seemed less elegant, but the exclusive version might be faster.

Cheers, Heiko

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Re^2: Range check with unordered limits
by syphilis (Archbishop) on Jul 13, 2022 at 08:23 UTC
    $inRange = ($x > $a == $x < $b) || $x == $a || $x == $b; (inclusive)

    Two thoughts:

    1) Isn't that equivalent to: 
    $inRange = ($x >= $a == $x <= $b);

    [download]
    Update: Yes, it isn't ;-) Thanks LanX.

    2) Is it safe to assume that ($x > $a) and ($x < $b) will return the same value whenever they are true ?
    It probably is ... but the docs merely say that they will return a true value, with no explicit guarantee that the magnitude of the "true value" will always be the same.

    Cheers,
    Rob
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      > 1) Isn't that equivalent to:

      No, your version fails the limits when they are swapped

      Here a generalized test suite for everyones experiments:

      use v5.12;
use warnings;

our ($a,$b,$x);

for my $lim ( [2,4], [4,2] ) {
    ($a,$b) = @$lim;
    for $x (1..5) {
        my @r = (&s0,&s1);
        unless ( $r[0] == $r[1] ) {
            say "fails for $x in [@$lim] with <$r[0]>,<$r[1]>";
        }
    }
}

sub s0 {
    ($x > $a == $x < $b) || $x == $a || $x == $b;
}

sub s1 {
    $x >= $a == $x <= $b;
}

      [download]

      c:/tmp/pm/clever_intervall.pl 
fails for 2 in [4 2] with <1>,<>
fails for 4 in [4 2] with <1>,<>

      [download]

      Cheers Rolf
      (addicted to the Perl Programming Language :)
      Wikisyntax for the Monastery

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Re^2: Range check with unordered limits
by LanX (Saint) on Jul 13, 2022 at 09:19 UTC
    > I agree with ... LanX that ... is the most canonical form

    Did I say this?

    Cheers Rolf
    (addicted to the Perl Programming Language :)
    Wikisyntax for the Monastery

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      IMHO for a multiplying approach that's the best check, even for the <=> version.
      So not verbally, but you preferred this version, I understood (as I do now).
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Re^2: Range check with unordered limits
by hexcoder (Curate) on Jun 08, 2024 at 09:36 UTC
    $inRange = ($a <=> $x) != ($b <=> $x); looks good too.
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In Section Cool Uses for Perl