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GitHub - eeue56/derw: An Elm-inspired language that transpiles to TypeScript

 2 years ago
source link: https://github.com/eeue56/derw
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An Elm-inspired language that transpiles to TypeScript

Usage

You can run the derw compiler via npx. You must provide files via --files.

npx @eeue56/derw

Compiles Derw code
Provide entry files via --files
  --files [string...]:      Filenames to be given
  --target ts | js | derw:	Target either TS or JS output
  --output string:		    Output directory name
  --verify :		        Run typescript compiler on generated files to ensure valid output
  --debug :		            Show a parsed object tree
  --only string:		    Only show a particular object
  --run :		            Should be run via ts-node/node
  --format :		        Format the files given in-place
  -h, --help :		        This help text

Example

You can find a bunch of examples in examples, along with the Typescript they generate. But the general gist is: Elm-compatible syntax where possible.

type Result a b
    = Err { error: a }
    | Ok { value: b }

asIs : Result a b -> Result a b
asIs result =
    case result of
        Err { error } -> Err { error }
        Ok { value } -> Ok { value }

Roadmap

0.0.1 alpha

  • Arrays [ ], [ 1, 2, 3 ], [ [ 1, 2, 3 ], [ 3, 2, 1 ] ]
  • Booleans true, false
  • Boolean equality 1 < 2, 1 <= 2, 1 == 2, 1 != 2, 1 > 2, 1 >= 2
  • Boolean operations true && false, not true, true || false
  • Strings "", "hello world"
  • Format strings ``, `Hello ${name}`
  • Numbers -1, 0, 1, -1.1, 1.1
  • Addition 1 + 2, "Hello" + name
  • Subtraction 2 - 1
  • Multiplication 2 * 1
  • Division 2 / 1
  • Pipe [1, 2, 3] |> List.fold add, List.fold add <| [1, 2, 3]
  • Compose >>, <<
  • Constants hello = "hello world"
  • Function definitions
  • Lists [ 1, 2, 3 ], [ "hello", "world" ]
  • List ranges [ 1..5 ], [ start..end ]
add : number -> number -> number
add x y = x + y
  • Function calls
three = add 1 2
  • Module references
three = List.map identity [ 1, 2, 3 ]
  • Union types
type Result a b
    = Err { error: a }
    | Ok { value: b }
  • Type variables
type Thing a = Thing a
  • Type aliases
type User =
    { name: string }
  • Object literals
user: User
user = { name: string }
  • Imports
import List
import Result exposing (map)
  • Exports
exposing (map)
  • Let statements
sayHiTo : User -> string
sayHiTo user =
    let
        name = user.name
    in
        "Hello " + name

sayHelloTo : User -> string
sayHelloTo user =
    let
        getName: User -> string
        getName user = user.name
    in
        "Hello" + getName user
  • If statements
type Animal = Animal { age: number }
sayHiTo : Animal -> string
sayHiTo animal =
    if animal.age == 1 of
        "Hello little one!"
    else
        "You're old"
  • Case..of
type Animal = Dog | Cat
sayHiTo : Animal -> string
sayHiTo animal =
    case animal of
        Dog -> "Hi dog!"
        Cat -> "Hi cat!"
  • Destructing in case..of
type User = User { name: string }

sayHiTo : User -> string
sayHiTo user =
    case user of
        User { name } -> "Hi " + name + !"
  • List destructing
sayHiTo : List number -> string
sayHiTo xs =
    case xs of
        [] -> "Empty"
        x::ys -> "Hello " + x + (sayHiTo ys)
  • Constructing union types
type User = User { name: string }
noah = User { name: "Noah" }
  • lambdas \x -> x + 1, \x y -> x + y
  • Typescript output
  • Javscript output
  • Module resolution
  • Type checking
  • Syntax highlighting for editors

1.0.0

  • An automatic formatter with no options
  • A standard library
  • Support for Coed
  • Testing support via Bach
  • Benchmarking support via Mainc

Divergence from Elm

  • All top level consts or functions must have type definitions
  • Format strings ``
  • No need for module names in the module file itself. Use exposing instead

Editor language support

Currently VSCode syntax highlighting is supported by this extension: https://github.com/eeue56/derw-syntax. It is not on the marketplace because Microsoft account creation was down when I tried.

Instead, you can do:

git clone https://github.com/eeue56/derw-syntax
cp -r derw-syntax ~/.vscode/extensions/derw-syntax-0.0.1

derw which means oak. Oak is one of the native trees in Wales, famous for it's long life, tall stature, and hard, good quality wood. An English speaker might pronounce it as "deh-ru".


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