elm-syntax

Elm Syntax in Elm: for parsing and writing Elm in Elm.

How does this work?

When Elm code is parsed, it's converted into an Abstract Syntax Tree (AST). The AST lets us represent the code in a way that's much easier to work with when programming.

Here's an example of that: Code: 3 + 4 * 2 AST:

OperatorApplication
    (Integer 3)
    "+"
    (OperatorApplication
        (Integer 4)
        "*"
        (Integer 2)
    )

Notice how it forms a tree structure where we first multiply together 4 and 2, and then add the result with 3. That's where the "tree" part of AST comes from.

Getting Started

import Elm.Parser
import Html exposing (Html)

src : String
src =
    """module Foo exposing (foo)

foo = 1
"""

parse : String -> String
parse input =
    case Elm.Parser.parseToFile input of
        Err e ->
            "Failed: " ++ Debug.toString e

        Ok v ->
            "Success: " ++ Debug.toString v

main : Html msg
main =
    Html.text (parse src)

Used in:

• elm-review
• elm-codegen
• elm-analyse
• elm-xref
• elm-lens