Constrained genericity: Difference between revisions
Rename Perl 6 -> Raku, alphabetize, minor clean-up
Thundergnat (talk | contribs) (Rename Perl 6 -> Raku, alphabetize, minor clean-up) |
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-- We have declared Banana and Tomato as a Food.</lang>
The Tomato_Box can only contain tomatoes; the Banana_Box can only contain bananas. You can only create boxes of eatable objects.
=={{header|C sharp|C#}}==
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}
}
}</lang>
=={{header|C++}}==
{{works with|C++11}}
Uses static assertion to disallow instantiations on incorrect types
<lang c++>
template<typename T> //Detection helper struct
struct can_eat //Detects presence of non-const member function void eat()
{
private:
template<typename U, void (U::*)()> struct SFINAE {};
template<typename U> static char Test(SFINAE<U, &U::eat>*);
template<typename U> static int Test(...);
public:
static constexpr bool value = sizeof(Test<T>(0)) == sizeof(char);
};
struct potato
{ void eat(); };
struct brick
{};
template<typename T>
class FoodBox
{
//Using static assertion to prohibit non-edible types
static_assert(can_eat<T>::value, "Only edible items are allowed in foodbox");
//Rest of class definition
};
int main()
{
FoodBox<potato> lunch;
//Following leads to compile-time error
//FoodBox<brick> practical_joke;
}</lang>
Line 915:
nom..nom..nom
nom..nom..nom</pre>
=={{header|Nim}}==
<lang nim>type
Eatable = concept e
eat(e)
FoodBox[e: Eatable] = seq[e]
Food = object
name: string
count: int
proc eat(x: int) = echo "Eating the int: ", x
proc eat(x: Food) = echo "Eating ", x.count, " ", x.name, "s"
var ints = FoodBox[int](@[1,2,3,4,5])
var fs = FoodBox[Food](@[])
fs.add Food(name: "Hamburger", count: 3)
fs.add Food(name: "Cheeseburger", count: 5)
for f in fs:
eat(f)</lang>
=={{header|Objeck}}==
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}
}</lang>
=={{header|Objective-C}}==
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print MrG.WeightGain 'result 15.75
</lang>
=={{header|Phix}}==
Line 1,426 ⟶ 1,406:
All the tests pass. Look at the tests to see what generates an exception (i.e.
not allowed at runtime) and what does not.
=={{header|Raku}}==
(formerly Perl 6)
{{works with|Rakudo|2016.01}}
<lang perl6>subset Eatable of Any where { .^can('eat') };
class Cake { method eat() {...} }
role FoodBox[Eatable] {
has %.foodbox;
}
class Yummy does FoodBox[Cake] { } # composes correctly
# class Yucky does FoodBox[Int] { } # fails to compose
my Yummy $foodbox .= new;
say $foodbox.perl;</lang>
{{out}}
<lang>Yummy.new(foodbox => {})</lang>
=={{header|Ruby}}==
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