automatic int to short conversion - the HELL?

[Ary Borenszweig]

Jarrett Billingsley wrote:
> On Fri, Sep 19, 2008 at 9:29 AM, Ary Borenszweig <ary at esperanto.org.ar> wrote:
>> bearophile wrote:
>>> Ary Borenszweig:
>>>> No, no. In Java it's an error, an explicit cast is required.
>>>> http://www.programmersheaven.com/2/FAQ-JAVA-Type-Conversion-Casting
>>>> Which is perfect. It expresses the intents of the programmer:
>>> About such matters I suggest you all to also take a look at how Ada works.
>>> Ada was designed first of all to create reliable software, so avoiding
>>> casting-derived bugs too is essential.
>>> D tries to avoid some of the pitfalls of C, to be a language less
>>> bug-prone: casts is where D has to improve still in such regards. Time ago
>>> (when I was more a D newbie) I have already had a bug in my code because of
>>> a casting bug:
>>>
>>> import std.stdio;
>>> void main() {
>>>    int n = -5;
>>>    int[] a = [1, 2, 3];
>>>    writefln(a.length > n); // prints false
>>> }
>>>
>>> A well designed language, even a system language like Ada or D, must avoid
>>> such kinds of bugs, regardless the amount of ignorance of the programmer.
>> Wow. At first, I thought that was already fixed. Now I've written that code,
>> compiled it and run it and saw it gives false. Ok, I know a.length is an
>> uint because logically it cannot be negative. But... shouldn't it be an int
>> to avoid this kind of bugs?? You loose nothing doing this. You are never
>> going to need an array of 2147483647 positions, much less a bigger array.
>>
>> I've checked C#, which has uint as a type. The length of an array is an int,
>> not an unit. A much better choice.
> 
> signed-unsigned comparison is, I think, a slightly larger problem than
> the type of array.length ;)

But if the length of an array is an uint, if you compare it to an int 
then what bearophile has just shown might happen.

Now, if the length of an array is an int, but which is guaranteed to be 
always positive or zero, then if you compare it to an int or an unit, 
you always get the desired result.

Conclusion: you avoid a bug to happen at zero cost.

So... why not?