Print pure elm-syntax declarations as haxe code.

import Elm.Parser
import ElmSyntaxToHaxe

"""module Sample exposing (..)

plus2 : Int -> Int
plus2 n =
    n + ([ 2 ] |> List.sum)
"""
    |> Elm.Parser.parseToFile
    |> Result.mapError (\_ -> "failed to parse elm source code")
    |> Result.map
        (\syntaxModule ->
            [ syntaxModule ]
                |> ElmSyntaxToHaxe.modules
                |> .declarations
                |> ElmSyntaxToHaxe.haxeDeclarationsToFileString
        )
-->
Ok """..some type declarations and imports..
class Elm {
    ..some default declarations..

    static function sample_plus2(n:Float):Float {
        return basics_add(n, list_sum(List_Cons(2.0, List_Empty)));
    }
}
"""

To try it out, you can run this node script.

why haxe?

• it's pretty much a superset of elm which makes transpiling easy (good type inference, choice types, records, value-ish semantics)
• it has best-class platform support via transpilation (c++, c via hashlink, java, jvm, c#, js, ...)

be aware

• only a subset of elm is currently supported. not supported:
  • elm/regex, elm/file, elm/bytes, elm/http, elm/random, elm/url, elm/json, elm/parser, elm/virtual-dom, elm/html, elm/svg, elm/browser, elm/time, elm-explorations/markdown, elm-explorations/webgl, elm-explorations/benchmark, elm-explorations/linear-algebra
  • Platform, Platform.Cmd, Platform.Sub, Task, Process
  • record update, currying, ports, glsl, (>>) and (<<), extensible records of any kind inferred or annotated
  • accessing record fields before their type is concretely known can sometimes not be inferred by haxe. When I finish implementing type inference, this will be fixed.
  • ++ will default to List.append unless one of the arguments is a string literal. So e.g. use a ++ b ++ "" to append string variables (which is also faster in elm)
  • List.minimum, List.maximum, Basics.min, Basics.max will only work with numbers.
  • potential future candidates: Basics.clamp, Basics.degrees, Basics.turns, Basics.radians, Basics.logBase, Basics.toPolar, Basics.fromPolar, Basics.never, Basics.sin, Basics.cos, Basics.tan, Basics.asin, Basics.acos, Basics.atan, Basics.atan2, Basics.e, Basics.pi, List.map3/4/5, List.head, List.tail, List.partition, Char.toLocaleLower, Char.toLocaleUpper, Char.isAlpha, Char.isAlphaNum, Char.isDigit, Char.isOctDigit, Char.isHexDigit, Bitwise, Array. Any help appreciated!
• no checks are performed before transpiling to haxe. So if you don't add a compile check of your elm input, you might e.g. get a running program that circumvents an elm opaque type or phantom type, or a haxe program that can't be run
• not much care has been put into making the resulting code readable or even conventionally formatted and comments are not preserved

Please report any issues you notice <3