Constrained genericity: Difference between revisions

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let your_box = FloatBox.make_box_from_list [2.3; 4.5]</lang>

Unfortunately, it is kind of cumbersome in that, for every type parameter we want to use for this generic type, we will have to explicitly create a module for the resulting type (i.e. <tt>BananaBox</tt>, <tt>FloatBox</tt>). And the operations on that resulting type (i.e. <tt>make_box_from_list</tt>) are tied to each specific module.

=={{header|Perl 6}}==

=={{header|Perl 6}}=

{{incorrect|Perl 6|While now the conditioning on existence of eat function seems to be right, now instead of a generic type which can be instantiated for specific food types, there's one single foodbox variable where any type of food can be put in.}}

subset Eatable of Any where { .^can('eat') };

<lang perl6>subset Eatable of Any where { .^can('eat') };

⚫

my ~~Eatable~~ @foodbox;

class Cake { method eat() {...} }

</lang>

role FoodBox[Eatable ::T] {

has T %.foodbox;

}

class Yummy does FoodBox[Cake] { } # composes correctly

# class Yucky does FoodBox[Int] { } # fails to compose

⚫

my Yummy $foodbox .= new;

say $foodbox.perl;</lang>

Output:

<lang>Yummy.new(foodbox => {})</lang>

=={{header|PicoLisp}}==