Improve monadic syntax to support switch and case

[elmattic]

It could help to have support of switch and case/if inside monads. E.g. for a binary format reader:

Wasm.Reader.val_type: Wasm.Reader(Wasm.ValType)
  (rst)
  open rst
  let len = 1#32
  def f = ((rst)
    rst@offset <- U32.add(rst@offset, len)
  ) :: Wasm.Reader.State -> Wasm.Reader.State
  if Wasm.Reader.State.ensure_bounds(rst, len) then
    let byte = Buffer8.get(rst.offset, rst.buffer)
    switch U8.eql(byte) {
      Wasm.Encoding.i32: Wasm.Reader.Reply.value!(f(rst), Wasm.ValType.i32),
      Wasm.Encoding.i64: Wasm.Reader.Reply.value!(f(rst), Wasm.ValType.i64),
      Wasm.Encoding.f32: Wasm.Reader.Reply.value!(f(rst), Wasm.ValType.f32),
      Wasm.Encoding.f64: Wasm.Reader.Reply.value!(f(rst), Wasm.ValType.f64),
    } default Wasm.Reader.Reply.fail!(
      rst.start,
      rst.offset,
      Wasm.Reader.Error.Code.invalid_val_type
    )
  else
    let code = Wasm.Reader.Error.Code.unexpected_end
    Wasm.Reader.Reply.fail!(rst.start, rst.offset, code)

It could be rewritten maybe as:

Wasm.Reader.val_type: Wasm.Reader(Wasm.ValType)
  Wasm.Reader {
    get byte = Wasm.Reader.u8
    switch U8.eql(byte) {
      Wasm.Encoding.i32: return Wasm.ValType.i32,
      Wasm.Encoding.i64: return Wasm.ValType.i64,
      Wasm.Encoding.f32: return Wasm.ValType.f32,
      Wasm.Encoding.f64: return Wasm.ValType.f64,
    } default Wasm.Reader.fail("Expected a Value Type")
  }

[VictorTaelin]

I'm thinking about that, but that would be different to the way Haskell does it. I'm not sure if there is a good reason not to do that.

[algebraic-dev]

Closed because the repository now only contains the code for the Kind2 language.