Is it possible to override the behavior of a type when used in a conditional expression?

[ag0aep6g via Digitalmars-d-learn]

On 09/10/2016 04:10 PM, pineapple wrote:
> I've got a struct and it would be very convenient if I could specify
> what happens when I write `if(value)` - is this possible?

`if (value)` implies a cast to bool. Define opCast!bool and it gets called:

----
struct S
{
     bool opCast(T : bool)() { return true; }
}
void main()
{
     S value;
     import std.stdio: writeln;
     if (value) writeln("yup");
}
----