Apply / Splat for Nim

apply.nim

import macros
proc mysum(a, b, c, d:int) =
  echo a + b + c + d

macro apply(fun, args: typed): untyped =
  result = newCall(fun)
  var funArgLen = getType(fun).len - 2
  case args.kind:
    of nnkBracket:
      for a in args:
        result.add a
    of nnkPrefix:
      if args[0].repr == "@":
        for a in args[1]:
          result.add a
    of nnkTupleConstr:
      for a in args:
        result.add a
    of nnkSym:
      for i in 0..<funArgLen:
        var b = newTree(nnkBracketExpr)
        b.add args
        b.add newLit(i)
        result.add b
    else: 
      #echo args.astGenRepr
      discard
  
let myarr = [1, 2, 3, 4]
mysum.apply(myarr)
mysum.apply([5, 6, 7, 8])

mysum.apply(@[9, 10, 11, 12])
let myseq = @[1, 2, 3, 4]
mysum.apply(myseq)

mysum.apply((1, 2, 3, 4))
let mytup = (5, 6, 7, 8)
mysum.apply(mytup)