-- TODO: support modules as macros?
--       does it make sense to store a constant AST as a macro?

-{ extension 'match' }

dollar = rawget(getfenv(), 'dollar') or { }

local function dollar_builder(call)
   match call with
   | `Call{ `Id{name}, ... } -> return dollar[name](select(2, unpack(call)))
   | `Id{name} -> 
      local m = dollar[name]
      match type(m) with
      | 'function' -> return m()
      | 'table'    -> return m
      | 'nil'      -> error "No such macro registered"
      | t          -> error ("Invalid macro type "..t)
      end
   | _ -> error "Invalid $macro, '$' should be followed by an identifier or function call"
   end
end   

mlp.expr.prefix:add{ '$', prec = 100, builder = |_, x| dollar_builder(x) }
mlp.stat:add{ '$', mlp.expr, builder = |x| dollar_builder(x[1]) }