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Comment by huehehue | Hacker News Reader

Practically, it's quite common to not immediately know the divisor. In cases where the divisor is initially unknown but takes an imperceptible amount of time to compute it's better to render 0%. Otherwise you might get a flash of a full progress bar (for example) while the divisor is determined.

Of course, it's context dependent. As others mention, your code might be full of stuff like X / (divisor || 1).

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The nicest UX would be to say something like "waiting..." while the denominator is zero. Presenting a zero to the user instead is probably an acceptable short-cut, but at the end of the day, it's a UX decision. Which is why it should be handled in explicit if-else code, that lives as close to the UI as possible, rather than being buried in the semantics of basic numerical operators.

If you dont know the number of elements, shouldnt that be tracked in another variable, instead of reusing the total elements variable and assuming 0 elements means unknown?

Also, if loading total elements takes a significant amount of time, shouldnt this loading also be reflected in the progess bar?

I’ve run into this a bit with progress related stuff. I bet if you looked at progress bar libraries they’d have similar logic built in.

    X / (divisor || 1).

It's invalid code in C, C++ and Java.

Boolean operators returning values is common, especially in dynamically typed languages. The code is valid in JavaScript, for example, and in Python (except it uses "or" instead of "||").

In python, it should probably be corrected with // or 1.0 to make it either an integer division or a float division.

Ah, that's true. Good point.

This is valid C and C++.

It is, but it will always give you a divisor of 1 (because "true" is 1 -- I also thought it would work until I tested it):

    % cat >division.c <<EOF
    #include <stdio.h>
    
    int main(void)
    {
            printf("1/0 = %d\n", 1 / (0 || 1));
            printf("1/2 = %d\n", 1 / (2 || 1));
    
            printf("1.0/0 = %f\n", 1.0 / (0 || 1));
            printf("1.0/2 = %f\n", 1.0 / (2 || 1));
    }
    % gcc -Wall -o divison divison.c
    % ./divison
    1/0 = 1
    1/2 = 1
    1.0/0 = 1.000000
    1.0/2 = 1.000000

In Python this is not the case:

    % python3
    >>> 1 / (0 or 1)
    1
    >>> 1. / (0 or 1)
    1.0
    >>> 1 / (0 or 1)
    1
    >>> 1. / (2 or 1)
    0.5
    % python3
    >>> 1 / (0 or 1)
    1.0
    >>> 1 / (2 or 1)
    0.5

Some trivia: GNU extensions to C/C++ include a "?:" operator that does what you'd want in this case, e.g.

    x / (divisor ?: 1)

It shouldn't be valid in C++. booleans cannot participate in arithmetic operations. You will get a warning from the compiler if you are lucky.

C doesn't have booleans and treat them as integers 0 or 1, it can do the math and will always return 1.

That's not true. C++ does define an implicit conversion from bool to int:

https://en.cppreference.com/w/cpp/language/implicit_conversi... (under "Integral promotion")

And C has a boolean type as of C99.

What do you expect for that C code?

In the context of this discussion, the idea was that it would act the same way as Python. But it obviously doesn't.

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