1 local digit_set = {

2 ["0"] = true, ["1"] = true, ["2"] = true, ["3"] = true, ["4"] = true,

3 ["5"] = true, ["6"] = true, ["7"] = true, ["8"] = true, ["9"] = true

4 }

5

6 function parse.decimal(str, dest_type, options)

7 local str = parse._pre_fold(str)

8 local dest_type = dest_type or atom.number

9 local options = options or {}

10 if str == "" then

11 return nil

12 else

13 local decimal_shift = options.decimal_shift or 0

14 if decimal_shift == true then

15 decimal_shift = options.precision

16 end

17 local decimal_point = locale.get("decimal_point") or "."

18 local negative = nil

19 local int = 0

20 local frac = 0

21 local precision = 0

22 local after_point = false

23 for char in string.gmatch(str, ".") do

24 local skip = false

25 if negative == nil then

26 if char == "+" then

27 negative = false

28 skip = true

29 elseif char == "-" then -- real minus sign already replaced by _pre_fold

30 negative = true

31 skip = true

32 end

33 end

34 if not skip then

35 if digit_set[char] then

36 if after_point then

37 if decimal_shift > 0 then

38 int = 10 * int + tonumber(char)

39 decimal_shift = decimal_shift - 1

40 else

41 frac = 10 * frac + tonumber(char)

42 precision = precision + 1

43 end

44 else

45 int = 10 * int + tonumber(char)

46 end

47 elseif char == decimal_point then

48 if after_point then

49 return dest_type.invalid

50 else

51 after_point = true

52 end

53 elseif char ~= " " then -- TODO: ignore thousand seperator too, when supported by format.decimal

54 return dest_type.invalid

55 end

56 end

57 end

58 int = int * 10 ^ decimal_shift

59 if dest_type == atom.number or dest_type == atom.integer then

60 if dest_type == atom.integer and frac ~= 0 then

61 return atom.not_a_number

62 else

63 local f = int + frac / 10 ^ precision

64 if negative then

65 f = -f

66 end

67 return f

68 end

69 elseif dest_type == atom.fraction then

70 return atom.fraction(int * 10 ^ precision + frac, 10 ^ precision)

71 else

72 error("Missing or invalid destination type for parsing.")

73 end

74 end

75 end