EMathFn = proc (args: seq[float]): float {.noSideEffect.}

EMathFnLookup = Table[string, EMathFn]

EMathNode {.acyclic.} = ref object
  children*: seq[EMathNode]
  isFinal*: bool             ## used for parsing and validity check
  case kind*: EMathNodeKind
  of emnkLit:
      value*: float

  of emnkCall, emnkVar:
      ident*: string

  of emnkPrefix, emnkPostfix, emnkInfix:
      operator*: EMathOperator

  of emnkPar:
    nil
  

EMathNodeKind = enum
  emnkLit, emnkPar, emnkVar, emnkCall, emnkPrefix, emnkPostfix, emnkInfix

EMathOperator = enum
  emoPow = "^", emoMult = "*", emoDiv = "/", emoPlus = "+", emoMinus = "-",
  emoMod = "%", emoNotFact = "!", emoAnd = "&", emoOr = "|", emoLarger = ">",
  emoLargerEq = ">=", emoEq = "==", emoNotEq = "!=", emoAlmostEq = "~=",
  emoLessEq = "<=", emoLess = "<", emoAssign = "="

EMathToken = object
  slice*: Slice[int]
  case kind*: EMathTokenKind
  of emtkNumber:
      number*: float

  of emtkIdent:
      ident*: string

  of emtkOperator:
      operator*: EMathOperator

  else:
    nil
  

EMathTokenKind = enum
  emtkNumber, emtkOperator, emtkIdent, emtkOpenPar, emtkClosePar, emtkComma

EMathVarLookup = Table[string, float]

func inside(mn: EMathNode): EMathNode {....raises: [], tags: [].}

func left(mn: EMathNode): EMathNode {....raises: [], tags: [].}

func priority(mo: EMathOperator): int {....raises: [], tags: [].}

func right(mn: EMathNode): EMathNode {....raises: [], tags: [].}