Say I have used Typedef! to create some new type and I declare a variable, constant or enum of that type. Is there a way that I can express a literal value on the rhs without having to use casts, as that seems to defeat the point of the nice type safety?

I may be asking for the impossible or _illogical_ here. In any case, I still get to keep the nice feature of not being able to mix up types with assignment from one variable to another.

Specific example is

    mac_addr_48_t   my_mac_address = 0x112233445566uL;

Which now produces a compile time error after I changed to use an alias  = Typedef!uint64_t as opposed to just a straight alias = uint64_t earlier with no strong typing.

On Monday, 31 July 2017 at 07:16:25 UTC, Cecil Ward wrote:
> Say I have used Typedef! to create some new type and I declare a variable, constant or enum of that type. Is there a way that I can express a literal value on the rhs without having to use casts, as that seems to defeat the point of the nice type safety?
>
> I may be asking for the impossible or _illogical_ here. In any case, I still get to keep the nice feature of not being able to mix up types with assignment from one variable to another.
>
> Specific example is
>
>     mac_addr_48_t   my_mac_address = 0x112233445566uL;
>
> Which now produces a compile time error after I changed to use an alias  = Typedef!uint64_t as opposed to just a straight alias = uint64_t earlier with no strong typing.

If struct + alias this is not strong enough the only solution is see is a helper template à la "octal" or "hexString", i.e a static cally checked string.

On Monday, 31 July 2017 at 07:50:57 UTC, inevzxui wrote:
> On Monday, 31 July 2017 at 07:16:25 UTC, Cecil Ward wrote:
>> Say I have used Typedef! to create some new type and I declare a variable, constant or enum of that type. Is there a way that I can express a literal value on the rhs without having to use casts, as that seems to defeat the point of the nice type safety?
>>
>> I may be asking for the impossible or _illogical_ here. In any case, I still get to keep the nice feature of not being able to mix up types with assignment from one variable to another.
>>
>> Specific example is
>>
>>     mac_addr_48_t   my_mac_address = 0x112233445566uL;
>>
>> Which now produces a compile time error after I changed to use an alias  = Typedef!uint64_t as opposed to just a straight alias = uint64_t earlier with no strong typing.
>
> If struct + alias this is not strong enough the only solution is see is a helper template à la "octal" or "hexString", i.e a static cally checked string.

I suspect that I am asking for something that literally makes no sense at all. I wanted to try and avoid opening the door to allowing the following kind of typing error now, eg
    enum ip_address = 0x11223344;
    mac_addr_48_t my_mac = cast(mac_addr_48_t) ip_address;
as if we are going to the bother of introducing strong type checking with Typedef! then the last thing I want to do is encourage is a proliferation of casts.

I realise something else now too -

Issue 2: The thing is that I also immediately have to do a lot of work to make the simplest operators work anyway, such as in

    foreach( addr;  base_mac_address .. base_mac_address + range )

where the + operator is producing compile-time errors now.

So it just seems that the Typedef! feature immediately make life into a nightmare. I don't know if something based of the physical units module (using 'dimensionless' in this case) would work - perhaps it only handles floating point of various types? Or whether that would also involve a huge amount of work and still have issue 1 mentioned earlier. In any case, I have absolutely no clue how to even begin to start using the units module thing.

On Monday, 31 July 2017 at 08:53:10 UTC, Cecil Ward wrote:
> On Monday, 31 July 2017 at 07:50:57 UTC, inevzxui wrote:
>> [...]
>
> I suspect that I am asking for something that literally makes no sense at all. I wanted to try and avoid opening the door to allowing the following kind of typing error now, eg
>     enum ip_address = 0x11223344;
>     mac_addr_48_t my_mac = cast(mac_addr_48_t) ip_address;
> as if we are going to the bother of introducing strong type checking with Typedef! then the last thing I want to do is encourage is a proliferation of casts.
>
> [...]

Actually, it would be really nice to have some kind of safe initialisation helper that checks value ranges, as in this particular case I need to make sure that the literal 64-bit value fits in 48 bits.

On Monday, 31 July 2017 at 08:53:10 UTC, Cecil Ward wrote:
> [ ... ]
> I suspect that I am asking for something that literally makes no sense at all. I wanted to try and avoid opening the door to allowing the following kind of typing error now, eg
>     enum ip_address = 0x11223344;
> [ ... ]

Please have a look at the bigEndian function and BigEndian struct in SQLite-D

https://github.com/UplinkCoder/sqlite-d/blob/master/source/utils.d

The point here is writing your own struct and using alias-this yourself.
Then you only need a function to produce constants of the right type.
Such a function should be trivially CTFEable