Checking function parameters in Phobos

[Simen Kjærås]

On 22.11.2013 00:50, Meta wrote:
> On Thursday, 21 November 2013 at 22:51:43 UTC, inout wrote:
>> What if you have more that just one validation, e.g. Positive and
>> LessThan42?
>> Is Positive!LessThan42!int the same type as LessThan42!Positive!int?
>> Implicitly convertible?
>
> Allow multiple validation functions. Then a Validated type is only valid
> if validationFunction1(val) && validationFunction2(val) &&...
>
> Validated!(isPositive, lessThan42, int) validatedInt =
> validate!(isPositive, lessThan42)(34);
> //Do stuff with validatedInt

I believe inout's point was this, though:

   Validated!(isPositive, lessThan42, int) i = foo();

   Validated!(isPositive, int) n = i; // Fails.
   Validated!(lessThan42, isPositive, int) r = i; // Fails.

This is of course less than optimal.

If a type such as Validate is to be added to Phobos, these problems need 
to be fixed first.


> Or just pass a function that validates that the int is both positive and
> less than 42, which would be much simpler.



-- 
   Simen