make (a < b < c) illegal?

[Miles]

Walter Bright wrote:
> Right now, in D (as well as C and C++), when you see the expression:
> 
>     if (a < b < c)
> 
> what is your first thought?

In C, C++ and D, the way they are now, my first thought is the
programmer needs to be replaced.

> and that it does NOT
> mean ((a < b) && (b < c)).

In a perfect language, the language should understand exactly what the
programmer meant. I would love to be able to type thinks like:

	if (1 < x <= 10)...

It makes a lot of sense. Python, ruby and other languages take it correctly.

> and even if it was intentional, it raises such
> a red flag that it shouldn't be used anyway.

Someone doing this intentionally points to a bug in the D spec.

> Andrei has proposed (and I agreed) that this should be done away with in
> the language, i.e. comparison operators should no longer be associative.
>  It's a simple change to the grammar. If one really did want to write
> such code, it could be done with parentheses:
> 
>     if ((a < b) < c)

I don't think so. Considering a, b and c of scalar type, if (a < b)
returns a boolean result, it should NOT be comparable with a scalar.
This is why I insist again that not having a true boolean type in D is a
big minus.

In my opinion:

 (a < b < c)		-> (a < b) && (b < c)
 (a < b == c > d)	-> (a < b) && (b == c) && (c > d)
 ((a < b) < c)		-> ERROR: comparing non-scalar and scalar types