Constrained genericity: Difference between revisions

Line 1,263:

// This declares the generic "FoodBox" type,

// whose parameter must "Eatable" constraint.

// whose parameter must satisfy the "Eatable" constraint.

// The objects of this type contain a vector of eatable objects.

struct FoodBox<T: Eatable> {

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}

// This implements the functions associated to the "FoodBox" type.

// This implements the functions associated with the "FoodBox" type.

// It is not required, but here it is used

// This statement is not required, but here it is used

// to declare a handy "new" constructor.

impl<T: Eatable> FoodBox<T> {

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}

// This makes the primitive "char" type satisfy the "Eatable" constraint.

// This makes also the primitive "char" type satisfy the "Eatable" constraint.

impl Eatable for char {

fn eat() {}

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// This instantiate a "FoodBox" parameterized by the "char" type.

// It is allowed as "char" implements "Eatable".

// It is allowed, as "char" implements "Eatable".

let _fb2 = FoodBox::<char>::new();

// This instantiate a "FoodBox" parameterized by the "bool" type.

// It is NOT allowed as "bool" does not implement "Eatable".

// It is NOT allowed, as "bool" does not implement "Eatable".

//let _fb3 = FoodBox::<bool>::new();

}