Re: John Guttag's book - 2nd exercise. My attempt in Perl.

Maybe this subroutine:

use strict;
use warnings;

my @array = (-11,-13,4, 22, 17);
print find_max_odd(@array), "\n";
sub find_max_odd {
    my $max; 
    while ($max = shift) {
        last if $max % 2;
    }
    return "Not found" unless @array;
    while (my $current = shift) {
        next unless $current % 2;
        if ($current > $max) {
            $max = $current;
        }
    }
    return $max;
}
[download]

Update: As pointed out by AnoMonk below, these while loops have a bug when one of the array item is 0.I suggest a better for loop in another post below.

Comment on Re: John Guttag's book - 2nd exercise. My attempt in Perl. Download Code

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Re^2: John Guttag's book - 2nd exercise. My attempt in Perl. by KurtZ (Friar) on May 20, 2017 at 22:12 UTC
you can avoid the first loop if you change `if ($current > $max) {` to `if ( not defined $max or $current > $max) {` $max would simply stay undef if all values were even. no it's more complicated ... wait This should do: `use strict; use warnings; my @array = ( -11, -13, 4, 22, 17); print "Result: ",find_max_odd(@array) // "undefined", "\n"; sub find_max_odd { my $max; for (@_) { next unless $_ % 2; unless ( defined $max ) { $max = $_; next; } $max = $_ if $_ > $max; } return $max; }` [download] I was confused, but becaus eof short-circuiting of the or the first idea should do too: `use strict; use warnings; my @array = (-11,-13,4, 22, 17); print find_max_odd(@array), "\n"; sub find_max_odd { my $max; while (my $current = shift) { next unless $current % 2; if (not defined $max or $current > $max) { $max = $current; } } return $max // "undefined"; }` [download]	[reply] [d/l] [select]
Re^3: John Guttag's book - 2nd exercise. My attempt in Perl. by Laurent_R (Canon) on May 21, 2017 at 09:27 UTC
Yeah, KurtZ, I definitely agree with you that it can be made simpler (++), and I most likely wouldn't code this the way I have shown. I only suggested a solution that used only very basic Perl knowledge since it was what the OP was asking for. Also, having two loops did not bother me too much, since they're browsing the array items only once anyway.	[reply]
Re^2: John Guttag's book - 2nd exercise. My attempt in Perl. by Anonymous Monk on May 22, 2017 at 18:03 UTC
Should `while (my $current = shift)` be `while ( defined( my $current = shift ) )` ? Otherwise it seems to fail if `@array` contains 0.	[reply] [d/l] [select]
Re^3: John Guttag's book - 2nd exercise. My attempt in Perl. by Laurent_R (Canon) on May 22, 2017 at 19:19 UTC
Yes, Anonymous Monk, you're correct, this `while` loop has a bug when one of the values in the array is 0. IMHO, this array traversal should really be made with a `for` loop, as it is usually better to use a `for` loop to iterate over an array, but the OP did not specify very clearly what was authorized and what not. This is what it might look like with a `for` loop. `use strict; use warnings; my @array = (-11,-13,4, 22, 17); print find_max_odd(@array), "\n"; sub find_max_odd { my $max; for my $num (@_) { next unless $num % 2; $max = $num unless defined $max; $max = $num if $num > $max; } return defined $max ? $max : "No odd number found\n"; # this co +uld be replaced with if conditional statements if needed }` [download]	[reply] [d/l] [select]