Hello Dlang community!

I need help in creating a template function which would look like the following pseudo-code:

    void foo(<a number>, <also a number>, <required arg>, <optional arg>...);
    // would be used as `void foo(x, y, arg1, arg2, ..., argN)`

    // valid examples:
    foo(5.332, 1, "a string", 123, "42");
    foo(3, 44, false);

    // invalid examples:
    foo(1, 1);
    foo(3, "stringers", "arg");

The underlying problems are:
* How do I ensure the two first arguments (used as coordinates) are types of numbers (all kinds: ints, floats, reals, etc.)
* At least one argument is passed after the coordinates

Best regards,
Vladimris Nordholm

On Sunday, 25 March 2018 at 18:24:37 UTC, Vladimirs Nordholm wrote:
> The underlying problems are:
> * How do I ensure the two first arguments (used as coordinates) are types of numbers (all kinds: ints, floats, reals, etc.)
> * At least one argument is passed after the coordinates

I found a solution which satisfies my needs :)

    void foo(X, Y, Args...)(X x, Y y, Args args)
    if (__traits(isArithmetic, x) && __traits(isArithmetic, y) && args.length >= 1)
    {
        // ...
    }

On Sunday, 25 March 2018 at 19:06:14 UTC, Vladimirs Nordholm wrote:
> On Sunday, 25 March 2018 at 18:24:37 UTC, Vladimirs Nordholm wrote:
>> The underlying problems are:
>> * How do I ensure the two first arguments (used as coordinates) are types of numbers (all kinds: ints, floats, reals, etc.)
>> * At least one argument is passed after the coordinates
>
> I found a solution which satisfies my needs :)
>
>     void foo(X, Y, Args...)(X x, Y y, Args args)
>     if (__traits(isArithmetic, x) && __traits(isArithmetic, y) && args.length >= 1)
>     {
>         // ...
>     }

FYI there's also https://dlang.org/library/std/traits/is_numeric.html incase you haven't see it -takes in to account bools and chars, which depending on your usecase you may not want to count as arithmetic.

Cheers
- Ali

On Sunday, 25 March 2018 at 21:31:16 UTC, aliak wrote:
> On Sunday, 25 March 2018 at 19:06:14 UTC, Vladimirs Nordholm wrote:
>> On Sunday, 25 March 2018 at 18:24:37 UTC, Vladimirs Nordholm wrote:
>>> The underlying problems are:
>>> * How do I ensure the two first arguments (used as coordinates) are types of numbers (all kinds: ints, floats, reals, etc.)
>>> * At least one argument is passed after the coordinates
>>
>> I found a solution which satisfies my needs :)
>>
>>     void foo(X, Y, Args...)(X x, Y y, Args args)
>>     if (__traits(isArithmetic, x) && __traits(isArithmetic, y) && args.length >= 1)
>>     {
>>         // ...
>>     }
>
> FYI there's also https://dlang.org/library/std/traits/is_numeric.html incase you haven't see it -takes in to account bools and chars, which depending on your usecase you may not want to count as arithmetic.
>
> Cheers
> - Ali

Thanks Ali, I had not thought about chars, bools, etc.

However I do not understand how to use that with my arguments. Eg. I would expect to do something like:

    void foo(X, Y, Args...)(X x, Y y, Args args)
    if(isNumeric!(x) && isNumeric!(y) && args.length >= 1)
    {
        // ...
    }

gives the error

    template instance isNumeric!(x) does not match template declaration isNumeric(T)

How would I resolve this issue?

On Monday, 26 March 2018 at 06:40:34 UTC, Vladimirs Nordholm wrote:

>
> However I do not understand how to use that with my arguments. Eg. I would expect to do something like:
>
>     void foo(X, Y, Args...)(X x, Y y, Args args)
>     if(isNumeric!(x) && isNumeric!(y) && args.length >= 1)
>     {
>         // ...
>     }
>
> gives the error
>
>     template instance isNumeric!(x) does not match template declaration isNumeric(T)
>
> How would I resolve this issue?


isNumeric applies to a type, not to a variable => IsNumeric!X

On Monday, 26 March 2018 at 06:40:34 UTC, Vladimirs Nordholm wrote:
> How would I resolve this issue?

use the type not the variables:
isNumeric!X && isNumeric!Y

On Monday, 26 March 2018 at 06:48:45 UTC, rumbu wrote:
> isNumeric applies to a type, not to a variable => IsNumeric!X

On Monday, 26 March 2018 at 06:51:48 UTC, arturg wrote:
> use the type not the variables:
> isNumeric!X && isNumeric!Y

Ah, missed that. Thanks a bunch!