SMLでレンジリテラルっぽいの

range.sml

datatype range
  = to of int * int
  | below of int * int

infix to below

structure List = struct
open List

local
    fun fromRangeSub (cmp, x, y) = let
        fun loop (i, acc) = if cmp(i, y)
                     then loop(i+1, i :: acc)
                     else List.rev acc
    in
        loop (x, [])
    end
in
fun fromRange (x to y) = fromRangeSub(op<=, x, y)
  | fromRange (x below y) = fromRangeSub(op<, x, y)
end
end

val list = List.fromRange(1 to 100)