David (>), Jonathan on Rakudo.org (>>):
>> Applied a patch from bacek++ to get "min= and "max=" working ("$foo min=
>> 100" will assign 100 to $foo if it's smaller than what is in $foo).
>
> Nice -- except I first read that backwards, i.e. even though it follows
> straight from the definition of "[op]=", it made me think of forcing a
> minimum value, which would actually be max=.
>
> I can think of a few ways to deal with this:
>
> 1) Get used to it. Maybe document it somewhere to catch fewer people
> off-guard, but otherwise simply expect people to check their code.
For what it's worth, I write a lot of Perl 6, and I'm already used to
it. I don't think it's backwards, and hence I don't think any action
need be taken to reverse its meaning or go out of one's way to find
other ways to say the same thing.
I simply read '$foo min= 100' as 'set $foo to the minimum of itself
and 100', just as I think of '$foo += 100' as 'set $foo as the sum of
itself and 100'.
> 3) Avoid the potential for confusion by having another way to set min/max
> values, such as:
> $foo.min = 100;
> min($foo) = 100; # lvalue function
> $foo = get-foo() :min(100); # adverb on =
>
> I'm not crazy about any of those, but that did suggest what is probably a
> better way to approach it anyway: setting limits at declaration rather than
> repeating them every time the variable is assigned to:
>
> my $foo is limited(100..200);
> $foo = 5; # really does $foo = 100
Sounds like a good idea for a CPAN module. You can already do
something similar with the subset keyword, though:
subset Percentage of Int where { 0 <= $^perc <= 100 };
sub set_percentage(Percentage $perc is rw, Int $value) {
try {
return $perc = $value;
CATCH {
return $perc = 0 if $value < 0;
return $perc = 100
}
}
};
my Percentage $p;
say set_percentage($p, 50);
say set_percentage($p, 101)
// Carl
