Mirror of forum.nim-lang.org

548 :: Problem with succ(bool)

• sanjay (orginal) [2014-09-04T17:38:41+02:00] view original

  For bool, the succ() is not giving the right output whereas the pred() does.

  echo(succ(true))    # true - should be false
  echo(succ(false))   # true
  echo(pred(true))    # false
  echo(pred(false))   # true
  Run

---

• Araq (orginal) [2014-09-04T18:03:21+02:00] view original

  I'm pretty sure they are both wrong. The problem is that range checks are missing and so succ(true) produces bool(2). It's an old and somewhat unresolved issue because proper range checks prevents code like for x in false..true from working. (Think about it.) There is of course a way to make it work but this results in an unacceptable performance overhead.

---

• sanjay (orginal) [2014-09-04T19:15:41+02:00] view original

  Frankly speaking, succ() and pred() does not have any major usage for bool. May be it should not be supported.

---