3 ms·

Without the low int the even/odd theorem falls apart for wrap around I've definitely seen algorithms that rely upon that. I would agree, whether error values a

• School-Cotton 10mo ago
  What is the "even/odd theorem" ?
  • ratmice 10mo ago
    that all integers are either even or odd, and that for an even integer that integer + 1 and - 1 are odd and vice versa for odd numbers. That the negative numbers have an additional digit from the positive numbers ensures that low(integer) and high(integer) have different parity. So when you wrap around with overflow or underflow you continue to transition from an even to odd, or odd to even.
    • xigoi 10mo ago
      If you need wraparound, you should not use signed integers anyway, as that leads to undefined behavior.
      • ratmice 10mo ago
        Presumably since this language isn't C they can define it however they want to, for instance in rust std::i32::MIN.wrapping_sub(1) is a perfectly valid number.
        • xigoi 10mo ago
          Nim (the original one, not Nimony) compiles to C, so making basic types work differently from C would involve major performance costs.
          • beagle3 10mo ago
            And yet, Nim does overflow checking by default.
      • School-Cotton 10mo ago
        Signed overflow being UB (while unsigned is defined to wrap) is a quirk of C and C++ specifically, not some fundamental property of computing.
        • xigoi 10mo ago
          Nim (the original one, not Nimony) compiles to C, so making basic types work differently from C would involve major performance costs.
          • School-Cotton 10mo ago
            > making basic types work differently from C would involve major performance costs. Not if you compile with optimizations on. This C code: int wrapping_add_ints(int x, int y) { return (int)((unsigned)x + (unsigned)y); } Compiles to this x86-64 assembly (with clang -O2): wrapping_add_ints: lea eax, [rdi + rsi] ret Which, for those who aren't familiar with x86 assembly, is just the normal instruction for adding two numbers with wrapping semantics.
          • ratmice 10mo ago
            Presumably unsigned want to return errors too? Edit: I guess they could get rid of a few numbers... Anyhow it isn't a philosophy that is going to get me to consider nimony for anything.
        • Symmetry 10mo ago
          Specifically, C comes form a world where allowing for machines that didn't use 2's compliment (or 8 bit bytes) was an active concern.
          • aw1621107 10mo ago
            Interestingly, C23 and C++20 standardized 2's complement representation for signed integers but kept UB on signed overflow.
          • Asooka 10mo ago
• Mond_ 10mo ago
  Meh, you also see algorithms that have subtle bugs because the author assumed that for every integer x, -x has the same absolute value and opposite sign. I view both of these as not great. If you strictly want to rely on wraparound behavior, ideally you specify exactly how you're planning to wrap around in the code.