> On 13 Sep 2018, at 23:21, ToddAndMargo <toddandma...@zoho.com> wrote:
> On 09/13/2018 12:29 PM, Elizabeth Mattijsen wrote:
>>> On 13 Sep 2018, at 20:47, ToddAndMargo <toddandma...@zoho.com> wrote:
>>> On 09/12/2018 10:09 AM, Larry Wall wrote:
>>>> Basically, ignore any advice to treat Nil as a normal value, because
>>>> it really is intended to represent the *absence* of a value as much as
>>>> possible. It's a bit like the way solid-state electronics treats "holes"
>>>> as if they were real particles, and gets away with it much of the time.
>>>> But not all the time, because the hole isn't real; it's the collective
>>>> behavior of everything around a thing that's missing.
>>>> So while you can test explicitly for Nil if you try hard enough, it's
>>>> better not to try at all, because lots of places internally are using
>>>> that Nil to select some kind of default behavior that might or might
>>>> not look like Nil afterwards.
>>>> It was probably a mistake to put Nil into the type hierarchy underneath
>>>> the Any type in the first place. It's more of a concept type like
>>>> Junction, so probably belongs outside of Any, which sits the top of the
>>>> "normal" object hierarchy.
>>>> These types are deeply magical. Whenever you find yourself trying to
>>>> use Nil or Junction as a normal value, you have to ask yourself whether
>>>> you're just Mickey Mouse falling into the Sorcerer's Apprentice trap.
>>>> Unless you're a wizard, with Nil and Junction it's better to cargo cult
>>>> a few common usages and stay the heck away the rest of the time.
>>>> Larry
>>>
>>> Hi Larry,
>>>
>>> Beautiful description! Almost magical! :-)
>>>
>>> I will stick with .defined that you suggested in another
>>> thread.
>> Another way to deal with Nil is to use “with”, especially if you don’t need
>> to do anything if the value is Nil:
>> with “foo”.index(“o”) -> $index {
>> say “Found at index $index”;
>> }
>> Documentation:
>> https://docs.perl6.org/language/control#index-entry-control_flow_with_orwith_without-with%2C_orwith%2C_without
>
> Where I typically have to deal with Nil's is when I
> am looping through something I read back from a system
> call. I never thought much of it when I was using bash,
> but when you see the raw stuff ...
>
> Not a Nil, but things read back and looped with split
> can be interesting too.
>
> $ p6 'my $x="\na\nb\nc\n"; for ( split "\n", $x ) -> $i {print "<$i>\n"};'
> <>
> <a>
> <b>
> <c>
> <>
>
> with beginning and ending new lines.
FWIW, a more Perl6ish way would be:
$ p6 'my $x="\na\nb\nc\n"; for $x.lines -> $i {print "<$i>\n"};'
