3.6 Applicative（应用函子）

8.12

接口
gen:Applicative

Applicative接口。

procedure
(applicative:ap fa fb) → Applicative?
fa : Applicative?
fb : Applicative?

Applicative最小实现。

因为racket没有泛型，另一个最小实现pure不需要提供，只是在使用时，需要明确指定。

procedure
(Applicative? a) → boolean?
a : any/c

是不是gen:Applicative实例。

procedure
(<*> fa fb) → Applicative?
fa : Applicative?
fb : Applicative?

Example:

> (<*> (list (const 1)) (list 1 2 3 4))
'(1 1 1 1)

procedure
(<* fa fb) → Applicative?
  fa : Applicative?
  fb : Applicative?
(*> fb fa) → Applicative?
  fb : Applicative?
  fa : Applicative?

Examples:

> (<* (list 1 2) (list 1 2 3 4))
'(1 2 1 2 1 2 1 2)
> (*> (list 1 2) (list 1 2 3 4))
'(1 2 3 4 1 2 3 4)