std.traits.isBoolean
Mike Parker
aldacron at gmail.com
Sun Feb 18 15:12:50 UTC 2018
On Sunday, 18 February 2018 at 14:52:37 UTC, Tony wrote:
> At
> https://dlang.org/library/std/traits/is_boolean.html
>
> it has:
>
>
> enum isBoolean(T) = is(BooleanTypeOf!T) && !isAggregateType!T;
>
> per:
> https://dlang.org/library/std/traits/is_aggregate_type.html
>
> isAggregateType is true for [struct, union, class, interface].
>
> So BooleanTypeOf!T is true for structs, unions, classes and
> interfaces? And if yes, why is that so?
Generally, no. But with alias this, it can be:
=====
import std.traits : BooleanTypeOf;
import std.stdio : writeln;
struct NoBool {
int x;
}
struct AliasThisBool {
bool b;
alias b this;
}
void main()
{
static if(is(BooleanTypeOf!NoBool)) writeln("NoBool");
static if(is(BooleanTypeOf!AliasThisBool))
writeln("AliasThisBool");
}
=====
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