Mirror of forum.nim-lang.org

10822 :: Is there a more elegant approach

• aiac (orginal) [2024-01-01T05:33:23+01:00] view original

  type PageNo = 1 .. 100
  
  var a: PageNo = 1
  
  a = if a == PageNo.low(): a  else:  (a - 1)
  a = if a == PageNo.low(): a  else:  (a - 1)
  
  echo a
   
  Run

---

• amadan (orginal) [2024-01-01T06:57:08+01:00] view original

  One way I can think of is using max

  type PageNo = 1 .. 100
  
  var a: PageNo = 1
  
  a = max(PageNo.low, a - 1)
  a = max(PageNo.low, a - 1)
  
  echo a
  Run

---

• Isofruit (orginal) [2024-01-01T11:10:41+01:00] view original

  Honestly your approach of "first check, then decrement" is working well enough. You can just refactor it for better readability. E.g.:

  type PageNo = 1 .. 100
  
  proc isFirstPage(x: PageNo): bool =
    x == PageNo.low()
  
  proc dec(x: var PageNo) =
    x = x - 1
  
  var a: PageNo = 1
  
  if not a.isFirstPage():
    a.dec
  
  if not a.isFirstPage():
    a.dec
  
  echo a
   
  Run

  Though that is more to stay true to your original design. You can also just move it all into dec to make it not error for bad inputs, which appears to be your intent:

  type PageNo = 1 .. 100
  proc isFirstPage(x: PageNo): bool =
    x == PageNo.low()
  
  proc dec(pageNum: var PageNo) =
    if not pageNum.isFirstPage():
      pageNum = pageNum - 1
  
  var a: PageNo = 1
  a.dec
  a.dec
  
  echo a
  Run

---