I'd like to do something like this:
    static if (is(Type.epsilon)) {
        // Type is fp type
        alias Type RType;
        static final bool isfloat = true;
    } else {
        // type is not fp type
        alias real RType;
        static final bool isfloat = false;
    }

I thought the is(Type.epsilon) would fail only if Type didn't have an epsilon, but it seems to fail no matter what.

Is there another way to achieve this other than enumeration of the float types, i.e.
 static if (is(Type==float) || is(Type==double) || is(Type==real))...

I'd rather use duck typing here, i.e. if it has some property that makes it float-like, then do one thing, otherwise do another.

Actually what I *really* want to do is just special case types for which a particular funtion is not defined.  E.g. sqrt().  If sqrt() doesn't exist for the type then I'd like to do something else (because it won't compile with the call to sqrt in there...)

Is there a way to achieve that other than the enumeration of the things I know have a sqrt?  Problem with that is a user can easily provide a sqrt for their type.  So I have no way of knowing in advance what types have sqrt functions and which don't.

--bb

Bill Baxter schrieb am 2006-10-24:
> I'd like to do something like this:
>      static if (is(Type.epsilon)) {
>          // Type is fp type
>          alias Type RType;
>          static final bool isfloat = true;
>      } else {
>          // type is not fp type
>          alias real RType;
>          static final bool isfloat = false;
>      }
>
> I thought the is(Type.epsilon) would fail only if Type didn't have an epsilon, but it seems to fail no matter what.

is(typeof(Type.epsilon))

> Actually what I *really* want to do is just special case types for which a particular funtion is not defined.  E.g. sqrt().  If sqrt() doesn't exist for the type then I'd like to do something else (because it won't compile with the call to sqrt in there...)
>
> Is there a way to achieve that other than the enumeration of the things I know have a sqrt?  Problem with that is a user can easily provide a sqrt for their type.  So I have no way of knowing in advance what types have sqrt functions and which don't.

sure:

static if(is(typeof(sqrt(Type.init)))){
	...
}

Thomas

Thomas Kuehne wrote:
> 
> is(typeof(Type.epsilon))

> static if(is(typeof(sqrt(Type.init)))){
> 	...
> }

Excellent!  Thanks.
--bb