Extended Type Design.

[Andrei Alexandrescu (See Website For Email)]

Alex Burton wrote:
> Andrei Alexandrescu (See Website For Email) Wrote:
> 
>> Walter Bright wrote:
>>> Derek Parnell wrote:
>> [snip]
>>>>> invariant
>>>>  This is applied to declarations to prevent code in the same 
>>>> application as
>>>> the declaration from being able to modify the item being declared.
>>> Almost right. It isn't the declaration, but the *type* that is 
>>> invariant. Invariant applies to the type, not the name.
>> By the way, "invariant" is a lifesaver. Everybody and their sister in 
>> the coffee shop liked it at the first sight. The girl at the counter 
>> asked for kris' email :o).
>>
>> Yes, "invariant" is essentially a synonym to "constant", but here are 
>> two simple mnemonic devices to remember which is which:
>>
>> a) "const" is shorter because it's used more often;
>>
>> b) "const" is similar to C++'s homonym.
>>
>> Easier to remember than perl's $|.
>>
>>
>> Andrei
> 
> Another option I'd like to have at least considered is the finding of a character that can be used to denote const.
> Adding various constnesses to all the code could easily add a whole lot of typing to the task of getting things done in D.
> 
> Could we find a unicode character that wouldn't be too much trouble for editors to insert ? Might mean that D starts to require unicode source - but is that such a bad thing ?
> 
> Are there any ascii characters that can be found that wont confuse the parser ? - like how the use of ! works for templates

Type inference will reduce the need for littering code with "const" a 
great deal (when compared to today's C++ code, at least). You just write:

auto var = expression;

and the const will propagate. Initial experience will show whether this 
is enough.


Andrei