Fuzion • Idioms • Idiom # 173: Format a number with grouped thousands

Idiom # 173: Format a number with grouped thousands

Code

format(x T : integer) String =>

    str:= x.as_string

    len := str.byte_length

    first :=
        if x < T.zero && len%3 = 1 then 4      # avoid separator right after minus
        else if len%3 > 0          then len%3  # determine size of first group
        else                            3
    
    groups(start i32, str String) String =>
        if start > (str.byte_length - 3)
        then ""
        else "," + (str.substring start (start + 3)) + groups (start + 3) str

    (str.substring (0) (first)) + (groups first str)

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format(x T : integer) String =>
    str:= x.as_string
    len := str.byte_length
    first :=
        if x < T.zero && len%3 = 1 then 4      # avoid separator right after minus
        else if len%3 > 0          then len%3  # determine size of first group
        else                            3
    
    groups(start i32, str String) String =>
        if start > (str.byte_length - 3)
        then ""
        else "," + (str.substring start (start + 3)) + groups (start + 3) str
    (str.substring (0) (first)) + (groups first str)
 
 
הההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההה
XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX

What are effects?

Running Example

ex173 is
  format(x T : integer) String =>

      str:= x.as_string

      len := str.byte_length

      first :=
          if x < T.zero && len%3 = 1 then 4      # avoid separator right after minus
          else if len%3 > 0          then len%3  # determine size of first group
          else                            3

      groups(start i32, str0 String) String =>
          if start > (str0.byte_length - 3)
          then ""
          else "," + (str0.substring start (start + 3)) + groups (start + 3) str0

      (str.substring (0) (first)) + (groups first str)


  numbers := [1, 42, 123, 1234, 12345, 123456, 1234567, 12345678, 123456789]

  for n in numbers
  do say "$n -> {format n}"

  for n in numbers
  do n_neg := n*(-1); say "$n_neg -> {format n_neg}"

  a := int i64.max
  say (format a*a)

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ex173 is
  format(x T : integer) String =>
      str:= x.as_string
      len := str.byte_length
      first :=
          if x < T.zero && len%3 = 1 then 4      # avoid separator right after minus
          else if len%3 > 0          then len%3  # determine size of first group
          else                            3
      groups(start i32, str0 String) String =>
          if start > (str0.byte_length - 3)
          then ""
          else "," + (str0.substring start (start + 3)) + groups (start + 3) str0
      (str.substring (0) (first)) + (groups first str)
  numbers := [1, 42, 123, 1234, 12345, 123456, 1234567, 12345678, 123456789]
  for n in numbers
  do say "$n -> {format n}"
  for n in numbers
  do n_neg := n*(-1); say "$n_neg -> {format n_neg}"
  a := int i64.max
  say (format a*a)
 
 
הההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההההה
XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX

What are effects?

last changed: 2025-05-13

next: NYI: Idiom # 174: Make HTTP POST request