Is it possible to create a function that returns Type like typeof() does? Something such as:

Type returnInt(){
    return int;
}

More to the point what is the Type of a type such as int?

Thanks

On Saturday, 16 January 2016 at 21:22:15 UTC, data pulverizer wrote:
> Is it possible to create a function that returns Type like typeof() does? Something such as:
>
> Type returnInt(){
>     return int;
> }
>
> More to the point what is the Type of a type such as int?
>
> Thanks

p.s. I am aware I could do typeof(1) to return int, but I am looking for something more elegant and some understanding.

On Saturday, 16 January 2016 at 21:22:15 UTC, data pulverizer wrote:
> Is it possible to create a function that returns Type like typeof() does? Something such as:
>
> Type returnInt(){
>     return int;
> }

Functions return values, not types. You would use a template to "return" a type.

>
> More to the point what is the Type of a type such as int?
>
> Thanks

What is the value of a value such as 9? A type is a type, it does not have a type.

If this is not clear, I can try to make it clearer.

On Saturday, 16 January 2016 at 21:22:15 UTC, data pulverizer wrote:
> Is it possible to create a function that returns Type like typeof() does? Something such as:
>
> Type returnInt(){
>     return int;
> }

No. A function cannot return a type. A template can evaluate to a type, though:

----
template returnInt(){
    alias returnInt = int;
}
----

> More to the point what is the Type of a type such as int?

Types don't have types. You can check if something is a type with an IsExpression: `is(T)` is true if T is a type.

On Saturday, 16 January 2016 at 21:22:15 UTC, data pulverizer wrote:
> Is it possible to create a function that returns Type like typeof() does? Something such as:
>
> Type returnInt(){
>     return int;
> }

A type itself isn't a runtime value.  I think the closest thing is a TypeInfo object:

https://dlang.org/library/object/type_info.html
https://dlang.org/spec/expression.html#TypeidExpression

On Saturday, 16 January 2016 at 21:59:22 UTC, data pulverizer wrote:
> On Saturday, 16 January 2016 at 21:22:15 UTC, data pulverizer wrote:
>> Is it possible to create a function that returns Type like typeof() does? Something such as:
>>
>> Type returnInt(){
>>     return int;
>> }
>>
>> More to the point what is the Type of a type such as int?
>>
>> Thanks
>
> p.s. I am aware I could do typeof(1) to return int, but I am looking for something more elegant and some understanding.

Thanks for all the answers. I guess I have been writing a lot of julia where I take creating arrays and tuples of types for granted. In this case types are of type DataType. I am aware that you can create tuples of types in D, but then it cannot be easily manipulated e.g. (int, float)[0] = string or similar. You have to immediately alias it and there are a limited number of operations you can do with the resulting type. I guess the constraints are that of a static language.

On 01/16/2016 02:50 PM, data pulverizer wrote:

> I guess I have been writing a lot of julia where I take
> creating arrays and tuples of types for granted. In this case
> types are of type DataType. [...] I guess the constraints are
> that of a static language.

Exactly. I am sure every D compiler has the equivalent of DataType and every type used in a program has instances of it but such information disappears by the end of compilation, except their properties in the form of TypeInfo as sarn has already mentioned.

Ali

On 01/16/2016 11:50 PM, data pulverizer wrote:
> I guess the constraints are that of a static language.

(This is not true.)

On Sunday, 17 January 2016 at 02:08:06 UTC, Timon Gehr wrote:
> On 01/16/2016 11:50 PM, data pulverizer wrote:
>> I guess the constraints are that of a static language.
>
> (This is not true.)

Could you please explain?

On 01/17/2016 08:09 PM, data pulverizer wrote:
> On Sunday, 17 January 2016 at 02:08:06 UTC, Timon Gehr wrote:
>> On 01/16/2016 11:50 PM, data pulverizer wrote:
>>> I guess the constraints are that of a static language.
>>
>> (This is not true.)
>
> Could you please explain?

E.g., a few of the systems discussed at

https://ncatlab.org/nlab/show/pure+type+system

would be a fine basis for a "static language" that supports returning types from functions.