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Comment by rweichler | Hacker News Reader

I see it as a toy language. The only person I think would find it useful is leafo himself since he can edit it however he wants. But everyone else should stay away from it. Plain Lua is so much better.

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Can't agree with that. Having used both Lua and Moonscript quite a bit I think Moonscript is what most dynamic scripting languages should be. Simple, succinct and does what you need for a scripting language.

I really enjoy using it.

Care to give an example?

The list comprehensions are really great. Most of the time when I'm writing Lua I can't be bothered to write exactly what Moonscript outputs for a list comprehension because it's noisy, but it's what I really would write if I cared about tiny amounts of performance.

Idk. Still not sold. You can do list comprehensions in regular Lua with something like this:

    function listcomp(t, f)
        local r = {}
        for k,v in pairs(t) do
            r[k] = v
        end
        return r
    end

And then, your Lua code would be like:

    listcomp({1, 2, 3, 4}, function(k, v)
        return v*2
    end)

Which would be the equivalent to this in MoonScript:

    [v*2 for k,v in pairs({1, 2, 3 ,4})]

I dunno. Just seems like a wash to me. And then you think about the extra compile step to run MoonScript, and the potential performance hits, and I'm just turned off completely from it.

There are no potential performance hits. In particular the code generated for list comprehensions would be faster than your example because there is no extra function call per item.

Over here it generated

  local b
  do
    local _accum_0 = { }
    local _len_0 = 1
    for k, v in pairs({
      1,
      2,
      3,
      4
    }) do
      _accum_0[_len_0] = v * 2
      _len_0 = _len_0 + 1
    end
    b = _accum_0
  end

It did a pretty good job. Unlike your code, it doesn't have any function calls, and unlike the code I would probably write, it doesn't use the # operator.

There are a lot of features that make Moonscript much more convenient than plain Lua. Examples (try the first three in Lua):

- default values for function parameters

- list comprehensions

    [x * 2 for x in *{1, 2, 3}]

- easier iteration (e.g. `for key, value in pairs obj`)

- local is default, not global

- a simple class system if you need it

- `export`, `from` and `import` keywords

- `+=`, `/=`, `*=` etc. operators

- indentation based scope (ok, this is debatable)

I can't think of a single place where plain Lua is actually better. OK maybe `:` is better as a method call operator, but that's it.

> default values for function parameters

    function f(a, b, c, d)
        a = a or 1
        b = b or 2
        c = c or 3
        d = d or 4
    end

> list comprehensions

https://news.ycombinator.com/item?id=14444215

> local is default, not global

I think this is a con.

> a simple class system if you need it

I also think this is a con, because it limits flexibility.

Here's my class system:

    Object = {}
    function Object:new()
        local self = setmetatable({}, {__index = self})
        return self
    end

And how to use it:

    local super = Object
    Shape = Object.new(super)
    function Shape:new(color)
        local self = super.new(self)
        self.color = color
        return self
    end

    local super = Shape
    RedShape = Object.new(super)
    function RedShape:new()
        local self = super.new(self, 0xff0000)
        return self
    end

If I want to add multiple inheritance, or interfaces, it is easy. Because it is just metatables. With MoonScript this is not possible.

> `export`, `from` and `import` keywords

Sounds like a con to me. `require` is simple.

> `+=`, `/=`, `*=`

I agree with this one.

    function f(a, b, c, d)
        a = a or 1
        b = b or 2
        c = c or 3
        d = d or 4
    end

Compare with:

    f = (a=1, b=2, c=3, d=4) -> ...

Also note the latter is correct when you call it as f(false).

It's a general purpose language, you never know who will use it and how.

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