Expressing range constraints in CNF form

[Steven Schveighoffer via Digitalmars-d]

On Monday, 12 June 2017 at 00:13:46 UTC, Adam D. Ruppe wrote:
> On Sunday, 11 June 2017 at 00:28:58 UTC, Andrei Alexandrescu 
> wrote:
>> // Also possible (no change to the language)
>> enum bool isInputRange(R) =
>>     is(typeof((ref R r) => r)) && msg("must be copyable")
>
>
> Or how about
>
> enum bool isInputRange(R) =
>       isCopyable!R &&
>       supportsBoolEmpty!R &&
>       supportsFront!R &&
>       supportsPopFront!R;
>
> and the compiler just calls out which condition didn't match?

Much better. Probably could be a bit more generic than that :)

>
>>     && is(typeof(lvalueOf!R.popFront)) && msg("must support 
>> back");
>
> hey look you already messed up the string by repeating it.

Exactly my point.

-Steve