Compile-time indexing of binary tree representation of multiprecision ints

stint_indexing.nim

import ../stint/private/datatypes
import macros

var a: UintImpl[UintImpl[uint64]]

proc asWordsImpl(x: NimNode, current_path: NimNode, result: var NimNode) =
  ## Transforms an UintImpl/IntImpl into an array of words
  ## at compile-time. Recursve implementation.
  ## Result is from most significant word to least significant

  let
    node = x.getTypeInst

  if node.kind == nnkBracketExpr:
    assert eqIdent(node[0], "UintImpl") or eqIdent(node[0], "IntImpl")

    let hi = nnkDotExpr.newTree(current_path, newIdentNode("hi"))
    let lo = nnkDotExpr.newTree(current_path, newIdentNode("lo"))
    asWordsImpl(node[1], hi, result)
    asWordsImpl(node[1], lo, result)
  else:
    result.add current_path

macro asWords*(x: UintImpl or IntImpl, idx: static[int]): untyped =

  var words = nnkBracket.newTree()
  asWordsImpl(x, x, words)

  result = words[idx]

echo a.asWords(2)

# macro asWords*(x: ForLoopStmt): untyped =
#   ## This unrolls the body of the for loop
#   ## and applies it for each word.

#   echo x.treerepr

#   # ##### Tree representation
#   # for word_a, word_b in asWords(a, b):
#   #   discard

#   # ForStmt
#   #   Ident "word_a"
#   #   Ident "word_b"
#   #   Call
#   #     Ident "asWords"
#   #     Ident "a"
#   #     Ident "b"
#   #   StmtList
#   #     DiscardStmt
#   #       Empty

#   # 1. Get the words variable idents and multiprecision ints ident to iterate on
#   var wordsIdents = nnkBracket.newTree
#   var idx = 0
#   while x[idx].kind == nnkIdent:
#     wordsIdents.add x[idx]
#     inc idx

#   var stintsIdents = nnkBracket.newTree
#   idx = 1
#   while idx < x[wordsIdents.len].len and x[wordsIdents.len][idx].kind == nnkIdent:
#     stintsIdents.add x[wordsIdents.len][idx]
#     inc idx

#   assert wordsIdents.len == stintsIdents.len, "The number of loop variables and multiprecision integers t iterate on must be the same"

#   # 2. For each stints, get the words from most significant to least significant
#   var words = nnkBracket.newTree
#   for ident in stintsIdents:
#     var wordList = nnkBracket.newTree()
#     asWordsImpl(ident, ident, wordList)
#     words.add wordList

#   result = words[0]

# for word_a, word_b in asWords(a, a):
#   discard