Missing python-like chaining in D

[Dom DiSc]

On Monday, 21 February 2022 at 09:48:53 UTC, Stanislav Blinov 
wrote:
> On Monday, 21 February 2022 at 09:29:56 UTC, forkit wrote:
>> It seems to me, that D is a language where python like 
>> chaining would be right at home.
>>
>> writeln(1 < 2 < 3 < 4 > 3 == 3); // true
>>
>
> I've no clue whatsoever how to interpret that mess, [...]

it means: eval each operator separately (so the operands in the 
middle are evaluated twice), then AND all the resulting booleans 
together and call that the result.
But that is something completely different from what C does. And 
D is meant to either do the same as C or don't compile the 
construct at all.
And as what C does is different from what math does, it was 
decided to not allow this to compile  to avoid code to silently 
change its meaning.

I fully agree with this decision because evaluating an operand 
twice is a behaviour that could have very bad side effects.  E.g. 
think of this:

if(1 < (x++) < 2)

Evaluating the middle operand twice will increment x by 2!! Is 
this desired?! And even if it is, will it be incremented first 
after checking if it is greater than one or after checking it if 
it is smaller than two? The result may be different, and as of 
yet there is no rule for this defined! Which one should it be, 
and why?