Fails(loop is not taken):

for(ulong i = len - 1; i >= (true) ? 0 : 1; i--)


passes

for(ulong i = len - 1; i >= ((true) ? 0 : 1); i--)

Only difference is parenthesis(yes, that is all, doesn't matter if it's true or false)

Brett wrote:

> Fails(loop is not taken):
>
> for(ulong i = len - 1; i >= (true) ? 0 : 1; i--)
>
>
> passes
>
> for(ulong i = len - 1; i >= ((true) ? 0 : 1); i--)
>
> Only difference is parenthesis(yes, that is all, doesn't matter if it's true or false)

not a bug. the whole thing before `?` is a condition, so

	i >= (true) ? 0 : 1

returns 0, of course, because `i >= 1` (your `len` is obviously >= 1), and the result of the expression is therefor 0.

On Tuesday, 17 September 2019 at 18:03:20 UTC, Brett wrote:
> for(ulong i = len - 1; i >= (true) ? 0 : 1; i--)
> for(ulong i = len - 1; i >= ((true) ? 0 : 1); i--)

Those are two different things by design. The >= binds more tightly than the ?:, it lets you do stuff like

a > 0 ? "greater than" : "not greater than"


Thus the first  one is more like

if(i >= (true)) {
  return 0;
} else {
  return 1; {
}

and the second one is

if(i >= ((true) ? 0 : 1)


Though I personally like to use extra parens though just remember that true and (true) are no different, regardless of context - those parens are totally redundant..

On Tuesday, 17 September 2019 at 18:06:55 UTC, ketmar wrote:
> Brett wrote:
>
>> Fails(loop is not taken):
>>
>> for(ulong i = len - 1; i >= (true) ? 0 : 1; i--)
>>
>>
>> passes
>>
>> for(ulong i = len - 1; i >= ((true) ? 0 : 1); i--)
>>
>> Only difference is parenthesis(yes, that is all, doesn't matter if it's true or false)
>
> not a bug. the whole thing before `?` is a condition, so
>
> 	i >= (true) ? 0 : 1
>
> returns 0, of course, because `i >= 1` (your `len` is obviously
> >= 1), and the result of the expression is therefor 0.

Makes sense, seems bad though... can introduce severe bugs in code if allowed. While using ?: there is not such a common idiom, using >= (or <= is)

Might be better for the compiler to detect such things and give a warning to use parenthesis? It could introduce subtle and hard to detect bugs.

Probably 99% of for loops use the syntax of var >= ...

I use it so much that way that I always think of ... as it's own expression rather than the entire part being an expression... it's my fault but I imagine 95% of programmers also think along similar ways. All it takes is forgetting this one time and one could have serious bugs(if the condition is complex and resolves in a hard to detect way it could produce such cases, rare but possible).

On Tuesday, 17 September 2019 at 18:16:41 UTC, Brett wrote:
> All it takes is forgetting this one time and one could have serious bugs(if the condition is complex and resolves in a hard to detect way it could produce such cases, rare but possible).

To be honest, your entire loop is one big code smell.

for(ulong i = len - 1; i >= ((true) ? 0 : 1); i--)

if len = 0, i will underflow and be initialized to ulong.max.
i >= 0 is vacuously true for an unsigned integer, resulting in and endless loop

I don't know your original situation, but if you can, please use foreach or foreach_reverse.

Brett wrote:

> Makes sense, seems bad though... can introduce severe bugs in code if allowed. While using ?: there is not such a common idiom, using >= (or <= is)
yeah. that's why ternary is not recommended to use -- it is not always obvious what is a condition there. ternary has one of the lowest priorities, and it is right-associative too.