The following result doesn't make sense to me... how does isInstanceOf return false?

```
import std.traits;
import std.stdio;
import std.typecons;
auto f(T)(T t){
	return Nullable!T(t); 	
}
void main(){
    auto f3 = f(3);
    writeln(typeof(f3).stringof);
    writeln(isInstanceOf!(Nullable, f3));
}
```

outputs

```
Nullable!int
false
```

On 1/30/20 4:51 PM, Ben Jones wrote:
> The following result doesn't make sense to me... how does isInstanceOf return false?
> 
> ```
> import std.traits;
> import std.stdio;
> import std.typecons;
> auto f(T)(T t){
>      return Nullable!T(t);
> }
> void main(){
>      auto f3 = f(3);
>      writeln(typeof(f3).stringof);
>      writeln(isInstanceOf!(Nullable, f3));
> }
> ```
> 
> outputs
> 
> ```
> Nullable!int
> false
> ```

In this case it's an instance of a type template, which only types would be. So, you want to check whether typeof(f3) is an instance of Nullable.

Ali

On Friday, 31 January 2020 at 00:51:45 UTC, Ben Jones wrote:
>     writeln(typeof(f3).stringof);
>     writeln(isInstanceOf!(Nullable, f3));

In the first one, you check typeof, but not in the second one.

    writeln(isInstanceOf!(Nullable, typeof(f3))); // true

The template argument there was T above - the type, not the value.