Checking function parameters in Phobos

[Simen Kjærås]

On 2013-11-25 13:00, Marco Leise wrote:
> Am Fri, 22 Nov 2013 02:55:44 +0100
> schrieb Simen Kjærås <simen.kjaras at gmail.com>:
>
>> 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.
>
> Can you write a templated assignment operator that
> accepts any Validated!* instance and builds the set difference
> of validation functions that are missing on the assigned value?
> E.g. in the case of n = i: {isPositive} / {isPositive,
> lessThan42} = emtpy set.

Do you mean this?

Validated!(int, isPositive, lessThan42) a =
     validated!(isPositive, lessThan42)(13);
Validated!(int, isPositive) b = a;
a = b; // Only tests lessThan42

If so, you're mostly right that this should be done. I am however of the 
opinion that conversions that may throw should be marked appropriately, 
so this will be the right way:

a = validated!(isPositive, lessThan42)(b); // Only tests lessThan42

New version now available on GitHub:
http://git.io/hEe0MA
http://git.io/QEP-kQ

--
   Simen