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digitalmars.D.learn - 2 little enigmas with is & Unqual!

reply spir <denis.spir gmail.com> writes:
Hello,

1. Why isn't Unqual!(char) =3D=3D char?
    writeln( is( Unqual!(typeof('c')) =3D=3D char ) );	// false
    writeln( is( Unqual!(char) =3D=3D char ) );		// false
    writeln( is( char =3D=3D char ) );			// true!
(dmd v2.049)

2. Why cannot one write "assert(is(Unqual(t1) =3D=3D t2))"?
    assert( is( char =3D=3D char ) );			// OK
    assert( is( Unqual!(char) !=3D char ) );		// compile Error
    assert( is( Unqual!(typeof('c')) !=3D char ) );	// compile Error
(is() gets on my nerves ;-)

Denis
-- -- -- -- -- -- --
vit esse estrany =E2=98=A3

spir.wikidot.com
Dec 01 2010
parent reply vincent picaud <vincent.picaud laposte.net> writes:
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


 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

hope this can help....


 Denis
 -- -- -- -- -- -- --
 vit esse estrany ☣
 
 spir.wikidot.com
Dec 01 2010
parent reply spir <denis.spir gmail.com> writes:
On Wed, 01 Dec 2010 10:03:57 -0500
vincent picaud <vincent.picaud laposte.net> wrote:


 spir Wrote:
=20

 Hello,
=20
 1. Why isn't Unqual!(char) =3D=3D char?
     writeln( is( Unqual!(typeof('c')) =3D=3D char ) );	// false
     writeln( is( Unqual!(char) =3D=3D char ) );		// false
     writeln( is( char =3D=3D char ) );			// true!
 (dmd v2.049)
=20


=20
 Using GCD 4.3.5 ( more precisely on Linux/Debian )
=20
     writeln( is( Unqual!(typeof('c')) =3D=3D char ) );      =20
     writeln( is( Unqual!(char) =3D=3D char ) );               =20
     writeln( is( char =3D=3D char ) );                       =20
=20
 returns=20
=20
 true
 true
 true
=20
 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) =3D=3D t2))"?
     assert( is( char =3D=3D char ) );			// OK
     assert( is( Unqual!(char) !=3D char ) );		// compile Error
     assert( is( Unqual!(typeof('c')) !=3D char ) );	// compile Error
 (is() gets on my nerves ;-)
=20


=20
 not sure of that, but I think "is" is a compile time feature, hence you m=


ust write

 static  assert( is( char =3D=3D char ) );			// OK
 static  assert( is( Unqual!(char)  =3D=3D char ) );		// OK
 static  assert( is( Unqual!(typeof('c'))  =3D=3D char ) );	// Ok


Well, on dmd:
    static  assert( is( Unqual!(char)  =3D=3D char ) );
raises:
    Error: static assert  (is(Unqual!(char) =3D=3D 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)  !=3D char ) );
yields:
    found '!=3D' when expecting ')'

Actually, i even cannot write:
    static  assert( is( char !=3D dchar ) );	// same error

Is this normal? Doesn't is() allow !=3D at all?=20


 hope this can help....


Yes, helps a lot, thank you Vincent.


Denis
-- -- -- -- -- -- --
vit esse estrany =E2=98=A3

spir.wikidot.com
Dec 01 2010
parent vincent picaud <vincent.picaud laposte.net> writes:
spir Wrote:


 On Wed, 01 Dec 2010 10:03:57 -0500
 vincent picaud <vincent.picaud 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?


Perhaps... I will check at home with dmd/windows, here I only  gdc/linux


 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? 


I think it is the right reason, is() does not support "!=", only "=="


 hope this can help....


 
 Yes, helps a lot, thank you Vincent.


Thank, I m a new comer here, :)



 
 
 Denis
 -- -- -- -- -- -- --
 vit esse estrany ☣
 
 spir.wikidot.com
Dec 01 2010