Compile time sequences

[Paul Backus]

On Wednesday, 3 October 2018 at 07:57:07 UTC, drug wrote:
> According to https://dlang.org/articles/ctarguments.html 
> compile time sequences "...allow a programmer to operate on 
> types, symbols and values..."
> Phobos has `isType`/`isTypeTuple` traits, also `isExpressions` 
> where expression may contain both values and symbols, but has 
> no traits like `isSymbol` and `isValue`. I handle this by 
> taking an address - values has no address, so I can distinct 
> types, symbols and values, but it's not convenient/consistent 
> way. I think it worths to add such traits, but probably I 
> missed something?

In my experience doing metaprogramming in D, it's best to make 
your static if/template constraint tests as narrow and specific 
as possible. For example, if you want to know whether you can 
call a function with a particular argument, you don't need to 
muck around with std.traits; you can just check whether the 
function call compiles:

     static if(__traits(compiles, f(arg))) {
         // do something with f(arg)
     }

So my question to you is: why do you care whether something is a 
symbol or a value? Is there actually a more specific question 
that you're trying to answer with that information? If so, just 
ask the more specific question directly.