On Thu, 8 Nov 2012 21:37:00 -0800
"H. S. Teoh" <[email protected]> wrote:
>
> IOW, you want the user-defined type to declare that it's an input
> range, and not just some random struct that happens to have input
> range like functions?
>
Yes.
> What about modifying isInputRange to be something like this:
>
> template isInputRange(R) {
> static if (R.implementsInputRange &&
> /* ... check for input range properties here
> */) {
> enum isInputRange = true;
> } else {
> enum isInputRange = false;
> }
> }
>
> Then all input ranges will have to explicitly declare they are an
> input range thus:
>
> struct MyInpRange {
> // This asserts that we're trying to be an input range
> enum implementsInputRange = true;
>
> // ... define .empty, .front, .popFront here
> }
>
Close. At that point you need two steps:
struct MyInpRange {
// Declare this as an input range
enum implementsInputRange = true;
// Enforce this really *IS* as an input range
static assert(isInputRange!MyRange,
"Dude, your struct isn't a range!"); // asserts
// ... define .empty, .front, .popFront here
}
My suggestion was to take basically that, and then wrap up the "Declare
and Enfore" in one simple step:
struct MyInpRange {
// Generate & mixin *both* the "enum" and the "static assert"
mixin(implements!InputRange);
// ... define .empty, .front, .popFront here
}
/Dreaming:
Of course, it'd be even nicer still to have all this wrapped up in
some language sugar (D3? ;) ) and just do something like:
struct interface InputRange {
// ... *declare* .empty, .front, .popFront here
}
struct interface ForwardRange : InputRange {
// ... *declare* .save here
}
struct MyForwardRange : ForwardRange {
// ... define .empty, .front, .popFront, .save here
// Actually validated by the compiler
}
Which would then amount to what we're doing by hand up above. So kinda
like Go, except not error-prone and ducky and all shitty.
