Type Declarations

All types in Irken are inferred, making Type declarations optional. However, there are many situations where type declarations can improve readability.

Here is an example of a function which takes two parameters of type int, and returns a string.

(define (my-function a b) : (int int -> string)
   (format (int a) " : " (int b)))

If you wish to return multiple arguments you can use a variant. Here we use a polymorphic variant with the empty name:

(define (my-function x) : (int -> (: int int))
   (: x (+x 1)))
(match (my-function 1) with (: a b) -> (printf (int a) " - " (int b)))

Parametric type parameters are preceded by a single quote ('), as in 'a.

(define (my-function x) : ('a -> 'a) 
      x)

Here are some other type examples:

(list 'a)                     ;; the parametric list type
(list int)                    ;; a list of int
(int -> #u)                   ;; a function taking one int and returning nothing (void)
{a=int b=string ...}          ;; an open record, matches any record with an integer "a"
                              ;;         field and string "b" field
{a=int b=string}              ;; a closed record, matches any record with exactly an a
                              ;;         and b field
(:vec int string)             ;; a polymorphic variant with an int and string
color                         ;; a static variant type (must match a datatype name)
|a=int|                       ;; a polymorphic variant row matching (:a int)
|a=int b=(int string)|        ;; a polymorphic variant row matching either (:a int) 
                              ;;         or (:b int string)