preparing for const, final, and invariant

[Ary Manzana]

I agree with you (althought I don't like your tone, but it's 
understandable).

I think D has in mind this sentence: "D is a language you should feel 
very comfortable in when writing applications, and that lets the user 
focus on his problem instead of fighting with the compiler". (I think I 
can recall a sentence like this one in a video about D given by Walter).

Well... with the problem of forward references this is not true. You 
focus on your problem until the compiler can't compile your code because 
you are using forward referneces. Then you have to fight with the 
compiler, try to hack it and trick it, to get your way. The const, 
final, scope keywords surely will help making code safer, but their lack 
doesn't prevent users from compiling their programs.

bobef escribió:
> Without any disrespect to the great work you are doing, let me put it in another way: In order to make a good, *usable* application, is this "const final scope" thing more important or having a good GUI library? There are not many console applications these days, you know. And they are not very *usable*. And, as we all know, choosing a GUI for D is not like choosing a GUI for C++. So why instead of adding nerd stuff to the language, make it sooooo much more *usable*, by fixing the reflection stuff that Tioport needs to produce libraries which are not 10mb or 20mb? Or... it kind of sucks when half of my code won't compile, or compiles in specific order only, because of some forward reference errors. I don't even know what forward reference is, but I know that using (simple) consts and aliases is something perfectly legal. I don't know if this second example is more usable than the final cosnt thing, just because I can't think of any use of it, but this is because I rarely u
se fancy stuff that breaks my code in the next version of DMD... But I am making this example to show that D (or DMD) still have so many things to fix the way it is now, we don't need some new fancy stuff before the old things work....
> 
> 
> Walter Bright Wrote:
> 
>> This is coming for the D 2.0 beta, and it will need some source code 
>> changes. Specifically, for function parameters that are arrays or 
>> pointers, start using 'in' for them.
>>
>> 'in' will mean 'scope const final', which means:
>>
>> final - the parameter will not be reassigned within the function
>> const - the function will not attempt to change the contents of what is 
>> referred to
>> scope - the function will not keep a reference to the parameter's data 
>> that will persist beyond the scope of the function
>>
>> For example:
>>
>> int[] g;
>>
>> void foo(in int[] a)
>> {
>>      a = [1,2];	// error, a is final
>>      a[1] = 2;   // error, a is const
>>      g = a;	// error, a is scope
>> }
>>
>> Do not use 'in' if you wish to do any of these operations on a 
>> parameter. Using 'in' has no useful effect on D 1.0 code, so it'll be 
>> backwards compatible.
>>
>> Adding in all those 'in's is tedious, as I'm finding out :-(, but I 
>> think the results will be worth the effort.
>