Allow default arguments

[skx]

I came across this example, recently:

(define*
 ;; function name: hi
 ;; a is needed
 ;; b has default argument 32
 ;; c has default argument "hi"
 (hi a (b 32) (c "hi"))
 ;; just returning the arguments
 (list a b c))

(list
 (hi 1)
 (hi :c 332 :a 3)
 (hi 3 2 1))

I'm not sure about the named-arguments, used when calling a function, but allowing default values for parameters seems nice and the syntax is trivial to handle.

[skx]

Reference:

• https://actondev.github.io/s7-playground/