Constrained genericity: Difference between revisions
J
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(J) |
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Line 252:
<lang haskell>instance (Food a) => Eatable a where
eat x = munch x</lang>
=={{header|J}}==
J is not a statically typed language, but I do not see why we should not implement this in J:
<lang j>coclass'Connoisseur'
isEdible=:3 :0
0<nc<'eat__y'
)
coclass'FoodBox'
create=:3 :0
assert isEdible_Connoisseur_ type=:y
collection=: 0#y
)
add=:3 :0"0
'inedible' assert type e. copath y
collection=: collection, y
)</lang>
An edible type would be a class that has a verb with the name 'eat'. For example:
<lang j>coclass'Apple'
eat=:3 :0
smoutput'delicious'
)</lang>
And here is a quicky demo of the above:
<lang j>
lunch=:(<'Apple') conew 'FoodBox'
a1=: conew 'Apple'
a2=: conew 'Apple'
add__lunch a1
add__lunch a2
george=: conew 'Connoisseur'
add__lunch george
|inedible: assert</lang>
=={{header|Java}}==
Line 276 ⟶ 315:
<lang java5>test.<EatableClass>bar();</lang>
The <code>foo</code> method from before can figure out <code>T</code> from its parameter, but this <code>bar</code> method needs to be told what T is.
=={{header|OCaml}}==
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