5 ms·

Here's another one. Handy "syntax" that makes it possible to iterate an unsigned type from N-1 to 0. (Normally this is tricky.) for (unsigned int i = N; i -->

• titzer 4y ago
  AFAICT this would parse as "(i--) > 0", there's no "-->" operator.
  • texaslonghorn5 4y ago
    https://stackoverflow.com/questions/1642028/what-is-the-operator-in-c https://stackoverflow.com/questions/1642028/what-is-the-oper...
• Jorengarenar 4y ago
  I was hesitant to put it on the list, but fine, you convinced me
• stonegray 4y ago
  If you're gonna test the i--, shouldn't it fall through on zero anyway? for (unsigned int i = N; i--;){} unsigned int i = N; while(i--){ ... } Also I think I'm missing the tricky part. Couldn't this be a bog-standard for loop? for (unsigned int i = N - 1; i > 0; i--){ ... } The "downto" pseudooperator definitely scores some points for coolness and aesthetics, but there's no immediately obvious use case for me.
  • Jorengarenar 4y ago
    The former executes loop when `i` is 0. And we cannot change the comparison to `>=` in the later, because unsigned is always bigger or equal 0, thus we would get infinite loop.
• skribanto 4y ago
  how would you iterate over every possible value of a unsigned int?
  • mtklein 4y ago
    Usually I use a do-while loop, unsigned char x = 0; do { printf("%d\n", x); } while (++x);
  • NoZebra120vClip 4y ago
    The unary complement operator should get you there: unsigned int x = 0; const unsigned int max = ~x; while (x <= max) { calc(x++); } Or, #include <limits.h> const unsigned int max = UINT_MAX;
    • kstenerud 4y ago
      Or if you only wanted to iterate halfway: unsigned int x = 0; while (x < ~x) { calc(x++); } Or going down: unsigned int x = ~0; while (x > ~x) { calc(x--); }
      • NoZebra120vClip 4y ago
        By "halfway", did you mean "off by one"?
        • kstenerud 4y ago
          no
    • mnaydin 4y ago
      This is equivalent to while (1) { calc(x++); } which is an infinite loop, since the expression x <= max is always true
      • NoZebra120vClip 4y ago
• deleted 4y ago
  [deleted]
• mtklein 4y ago
  It's worth noting that this does also work on signed types, so it can be a kind of handy idiom to see while (N --> 0) { ... } and know it will execute N times no matter the details of the type of N.