On Tuesday, 12 March 2013 at 14:16:15 UTC, H. S. Teoh wrote:
On Tue, Mar 12, 2013 at 12:39:48PM +0100, TommiT wrote:
On Tuesday, 12 March 2013 at 04:34:05 UTC, Walter Bright wrote:
>It's interfaces without the vtable[].
>
>It's still solely based on type signatures. D constraints make
>pretty much anything that can be computed at compile time a
>testable gate.
Yeah, you're right. That kind of interface syntax doesn't
really
lend itself to specifying concepts. So, here's another attempt
at
a concept syntax (and functionality):
concept AscendingInfiniteInputRange {
// 'this' is an instance of a type which implements the
// AscendingInfiniteInputRange concept given the
// if-condition below is true:
if( is(typeof(this.empty) : bool)
&& is(typeof(this.front))
&& !is(typeof(this.front) == void)
&& is(typeof(this.popFront() == void)
// testing a compile time evaluable value:
&& this.empty == false
// static members can also be tested:
&& typeof(this).infinite == true
&& typeof(this).sortedAscending == true )
}
How is this any different from the current isInputRange!R,
isForwardRange!R, etc.?
T
The difference is in function overload resolution. Polymorphic
concept based template would know about the hierarchical nature
of the concepts, say ForwardRange is a sub-concept of InputRange,
and thus the function overload resolution would be able to choose
the template which has the most derived/specialized concept
parameter that still matches with the given template argument.
