Typesafe variadics hack

gistfile1.nim

# Some generic functions that convert nimrod values to lua
proc push(ls: PState, s: string) = pushstring(ls, s)
proc push(ls: PState, i: int) = pushinteger(ls, i)
proc push(ls: PState, f: float) = pushnumber(ls, f)

# helpers for creating type safe variadic functions
proc argsToTuple(expr: PNimrodNode) : PNimrodNode {.compileTime.} =
  result = newNimNode(nnkPar)
  for i in 1..expr.len-1: add(result, expr[i])

template vararg_proc(name: expr, returnType: typeDesc, body: stmt) : stmt =
  proc `name NM_IMPL` [T](args : T) : returnType =
    body

  macro name (args: expr) : expr =
    var impl = toStrLit(args[0]).strVal & "NM_IMPL"
    result = newCall(!impl, argsToTuple(args))

# example generic function to perform arbitrary lua call
vararg_proc luaCall, int:
  var ls = args[0]

  # hack to deal with the limitation that we can't unroll on a subset of the tuple fields
  proc push(ls: PState, ls2: Pstate) {.inline.} = nil 

  for field in fields(args):
    push ls, field

  call(l, len(args) - 1)