unsigned policy (implicit conversions for complex?)

[Andrei Alexandrescu (See Website For Email)]

Frits van Bommel wrote:
> Joel C. Salomon wrote:
>> Walter Bright wrote:
>>> Derek Parnell wrote:
>>>> Characters are not numbers. 
>>>
>>> That's an enticing point of view, and it sounds good. But Pascal has 
>>> that view, and my experience with it is it's one of the reasons 
>>> Pascal sucks.
>>>
>>> Examples:
>>>
>>> 1) converting text <=> integers
>>> 2) converting case
>>
>> Neither are pointers numbers, but
>>     &a - &b
>> yields a usable number.  So long as
>>     x += c - 'a'
>> works, I don’t care if
>>     'a' * '3'
>> breaks.
> 
> Thank $DEITY. If nobody made this point before I read all of this 
> subthread I would have to write a long post explaining this.
> 
> Let me reiterate that: characters are to integers as pointers are to 
> integers.
> The difference between two pointers is an integer, and you can add 
> integers to pointers. These are the only arithmetic operations allowed 
> on pointers.
> The same should hold if you substitute 'character' for 'pointer' 
> everywhere in previous two sentences.
> 
> 
> Now, a short comment for each of the cases:
> 
> Walter Bright wrote:
>  > Examples:
>  >
>  > 1) converting text <=> integers
> 
> I don't see any reason why disallowing conversions from characters to 
> integers would disallow one to add or subtract integers from characters.
> So (for c of type char/wchar/dchar) c - '0' can still be an integer, for 
> example.
> But it makes absolutely no sense to be able to say c + '0'. Or c * '0'.
> 
>  > 2) converting case
> 
> As above, (c - 'A') + 'a' can still be allowed. (c - 'A') is an integer, 
> add 'a' to get a character again.
> 
>  > 3) doing compression/encryption code
> 
> These should probably use void[] for input and ubyte[] for output.
> 
>  > 4) using characters as indices (isspace() for example)
> 
> If you're using Unicode this is a bad idea anyway. Except perhaps if you 
> use a sparce associative array, and then this isn't a problem anyway.
> 
> If you insist on using a regular array (and make sure the character 
> value is suitably small) you don't necessarily have to use a cast, you 
> can also subtract '\0' if you prefer.
> 
> 
> Back to Joel:
>>> 4) using characters as indices (isspace() for example)
>>
>> Is there a way to declare the index type of an array?
> 
> Only if you use an associative array.

I think these are great ideas that could help us rethink the whole 
character handling business.


Andrei