8.12
Compact Annotations
| (require compact-annotations) | package: compact-annotations |
This library provides a more convenient syntax for writing typed racket polymorphic and curried functions. It is very similar to Haskell type annotations.
source code: https://github.com/jackfirth/compact-annotations
syntax
(:: id maybe-polymorphic function-type)
maybe-polymorphic =
| type-var-id ... => function-type = arg-type ... maybe-opt maybe-rest -> function-type | arg-type ... maybe-opt maybe rest -> result-type maybe-opt =
| + arg-type ... maybe-rest =
| * arg-type
Declares that id has the type determined by function-type,
which may be a parametric type over type-var-id ... if provided.
The syntax of function-type allows for partially applied function
types, optional argument types, and rest argument types.
With this syntax, the type of the identity function can be defined as follows:
Examples:
A function that takes one value and returns a function that takes another value
and ignores it, returning the first value can have it’s type defined as follows:
Examples:
Optional arguments can have their type specified with a +. For example,
a function that greets people with "Hello" by default can have it’s type defined
as follows:
Examples:
> (:: greet String + String -> String)
> (define (greet name [greeting "Hello"]) (string-append greeting " " name)) > (:print-type greet) (->* (String) (String) String)
> (greet "John") - : String
"Hello John"
> (greet "Jack" "Hey") - : String
"Hey Jack"
Rest arguments can also have their type specified with a *. A function
that converts it’s arguments from one type to String then appends them all
can have its type specified as follows:
Examples:
> (:: append-as-string A => (A -> String) * A -> String)
> (define (append-as-string a->string . as) (apply string-append (map a->string as))) > (:print-type append-as-string) (All (A) (-> (-> A String) A * String))
> (append-as-string number->string 1 2 3 4 5) - : String
"12345"