Tuple to function arguments in Nim

Question

Can I convert a tuple into a list of function arguments in Nim? In other languages this is known as "splat" or "apply".

For example:

proc foo(x: int, y: int) = echo("Yes you can!")

type:
  Point = tuple[x, y: int]

let p: Point = (1,1)

# How to call foo with arguments list p?

Answer 1

I haven't seen this in the stdlib or any other lib, but you can certainly do it yourself with a macro:

import macros

macro apply(f, t: typed): typed =
  var args = newSeq[NimNode]()
  let ty = getTypeImpl(t)
  assert(ty.typeKind == ntyTuple)
  for child in ty:
    expectKind(child, nnkIdentDefs)
    args.add(newDotExpr(t, child[0]))
  result = newCall(f, args)

proc foo(x: int, y: int) = echo("Yes you can!")

type Point = tuple[x, y: int]

let p: Point = (1,1)

# How to call foo with arguments list p?
apply(foo, p) # or:
foo.apply(p)

Further testing would be required to make sure this works with nested tuples, objects etc. You also might want to store the parameter in a temporary variable to prevent side effects from calling it multiple times to get each tuple member.