develooper Front page | perl.perl6.users | Postings from June 2018


Thread Previous | Thread Next
Trey Harris
June 14, 2018 20:13
Message ID:
Just a small stylistic thing to mention:

On Thu, Jun 14, 2018 at 1:59 AM Todd Chester <> wrote:

>        if not $dir.IO.d.bool {}
>        for  slice  "\n", $WebStr   ->  $Line { }
>   and on and on and so forth.  I know a lot of them by heart now.
By .bool, I assume you meant .Bool, but in any case, it isn’t necessary
since the context of a not forces it to be boolean.

If you want the opposite—a boolean without the sense-negation, you can use
so, but in the context of an if, it should rarely, if ever, be necessary.

In the same way that so is used to explicitly truthify, unary + is used to
explicitly numify.

E.g., once you know that an IntStr <>
dual value gives a result reminiscent of Perl 5’s string numbers (except
that without going to crazy lengths, you can easily supply exactly the
number and string you want):

my $x =, "The Answer");
my $y =, "Nothing");
for ($x, $y) -> $z {
  printf "\$z: '%s', so \$z: '%s', +\$z: '%s'\n",
                $z,        so $z,        +$z;
  say "  Double it: ", $z * 2;
  say "  or 'double' it: ", $z x 2;

gives results:

$z: 'The Answer', so $z: 'True', +$z: '42'
  Double it: 84
  or 'double' it: The AnswerThe Answer
$z: 'Nothing', so $z: 'False', +$z: '0'
  Double it: 0
  or 'double' it: NothingNothing

In case you’re wondering, you’ll usually have no reason to explicitly
construct a dual value like that; you generally get a NumStr or its
counterparts like IntStr when reading input or expecting command-line

(Also note that the stringification equivalent to so and unary + is ~, but
it wasn’t necessary above since the %s template to sprintf forces
stringification. Also note that using s/printf at all is not encouraged—but
it was useful above, just to make things explicit.)

Thread Previous | Thread Next Perl Programming lists via nntp and http.
Comments to Ask Bjørn Hansen at | Group listing | About