2 little enigmas with is() & Unqual!

[spir]

On Wed, 01 Dec 2010 10:03:57 -0500
vincent picaud <vincent.picaud at laposte.net> wrote:

> spir Wrote:
> 
> > Hello,
> > 
> > 1. Why isn't Unqual!(char) == char?
> >     writeln( is( Unqual!(typeof('c')) == char ) );	// false
> >     writeln( is( Unqual!(char) == char ) );		// false
> >     writeln( is( char == char ) );			// true!
> > (dmd v2.049)
> > 
> 
> Using GCD 4.3.5 ( more precisely on Linux/Debian )
> 
>     writeln( is( Unqual!(typeof('c')) == char ) );       
>     writeln( is( Unqual!(char) == char ) );                
>     writeln( is( char == char ) );                        
> 
> returns 
> 
> true
> true
> true
> 
> as expected

All right, I do not have the same results using dmd. Seems like abug, doesn't it?


> > 2. Why cannot one write "assert(is(Unqual(t1) == t2))"?
> >     assert( is( char == char ) );			// OK
> >     assert( is( Unqual!(char) != char ) );		// compile Error
> >     assert( is( Unqual!(typeof('c')) != char ) );	// compile Error
> > (is() gets on my nerves ;-)
> > 
> 
> not sure of that, but I think "is" is a compile time feature, hence you must write
> static  assert( is( char == char ) );			// OK
> static  assert( is( Unqual!(char)  == char ) );		// OK
> static  assert( is( Unqual!(typeof('c'))  == char ) );	// Ok

Well, on dmd:
    static  assert( is( Unqual!(char)  == char ) );
raises:
    Error: static assert  (is(Unqual!(char) == char)) is false
which is at least consistent with the result written above. But strangely, I cannot reverse the predicate:
    static  assert( is( Unqual!(char)  != char ) );
yields:
    found '!=' when expecting ')'

Actually, i even cannot write:
    static  assert( is( char != dchar ) );	// same error

Is this normal? Doesn't is() allow != at all? 

> hope this can help....

Yes, helps a lot, thank you Vincent.


Denis
-- -- -- -- -- -- --
vit esse estrany ☣

spir.wikidot.com