procprintf.nim

#import macros

import typetraits

type
  TokenKind = enum
    FInt, FString, Text
 
  Token = object
    case kind: TokenKind
    of FInt, FString: nil
    of Text: c: String
    
iterator tokenize(format: string): Token =
  var i = 0
  while True:
    case format[i]
    of '%':
      case format[i+1]
      of 'd': yield Token(kind: FInt)
      of 's': yield Token(kind: FString)
      of '\0': break
      else: echo("Incorrect format string.")
      i.inc
    of '\0': break
    else:
      yield Token(kind: Text, c: $format[i])
    i.inc
 

proc printf(format:string, params: varargs[int]): string = 
  var i = 0
  var stringLit = ""
  for tok in tokenize(format):
    case tok.kind
    of FInt:
      if i >= params.len: echo("Too many arguments in format string.")
      if params[i].type is int: echo("Expected Int got ", params[i].type.name)# " & $params[i].type)
      stringLit.add($params[i])
      i.inc
    of FString:
      if i >= params.len: echo("Too many arguments in format string.")
      if params[i].type is string: echo("Expected String got ", params[i].type.name)# & $params[i].type)
      stringLit.add($params[i])
      i.inc
    of Text: stringLit.add tok.c
  if i < params.len: echo("Too many arguments to printf.")
  result = stringLit
  
echo printf("%d", 1)

#Echos:

# Expected Int got int
# 1