default arguments as a macro

[Raynos]

It would be nice to figure out how to do default arguments in function declarations.

[jlongster]

This won't be too hard! I'm going to start adding more stuff in the next week or two.

[nmn]

Any updates? I'm struggling with the sweet.js syntax these days, or I'd just send some PRs your way.

[jlongster]

I've been using this project so far happily and have been working on a few other things. But I can come back and implement some of this stuff in the next week or so :)

[ponychicken]

See also: sweet-js/sweet-core#37

[ponychicken]

Here's a halfway working thing:

let function = macro {
  // Regular named functions
  rule { $name ($params ...) { $body }  } => {
    function $name split_params_comma ($params ...)  { split_params_space $params ... $body }
  }
  // Anon functions
  rule { ($params ...) { $body }  } => {
    function split_params_comma ($params ...)  { split_params_space $params ... $body }
  }
  // Bodyless functions
  rule { $name ($params ...) { }  } => {
    function $name split_params_comma ($params ...)  {}
  }
}

macro split_params_comma {
  rule { $param ... , $rest ... } => {
    remove_param_value $param ... , split_params_comma $rest ...
  }
  rule { $param ... } => {
    remove_param_value $param ...
  }
}

macro split_params_space {
  rule { $param ... , $rest ... } => {
    param_value_to_if $param ...  split_params_space $rest ...
  }
  rule { $param ... } => {
    param_value_to_if $param ...
  }
}

macro remove_param_value {
  rule { $name=$val } => { $name }
  rule { $name } => { $name }
}

macro param_value_to_if {
  rule { $name=$val } => { if (typeof $name == 'undefined') $name = $val; }
  rule { $name } => {  }
}

function Something(Test = 8) { a }

function Something(Test) { a }

function Something(Test, na = 9, ca = 9) { a }

function Something(Test, na = 9, ca = 9) {  }

Can someone figure out why anom fn are failing?