Re: is(this : myClass)
But with the current compiler you would never write
is(typeOf(myC) : typeof(c))
if in your mind "c" is actually a class "C" because if that is
in your mind you would just write
is(typeof(myC) : c)
which would get you the error. You only need typeof(variable)
to get to the type, there is no point in doing typeof(type),
you just write type and C is a type. Right?
But what value is evaluating a class type to a primitive type? It
will never be true? There has to be a reasonable chance for the
evaulation to be true for the 'is' operator to provide value. The
compiler should reject this 'is' statement or at minimum issue a
warning of incompatible types. This is nonsense creep of unusable
code (being able to write code that has no meaning and value).
This is equivalent to writing code like the following. It is just
more obfuscated:
if(false)
{
...
}
else
{
...
}
Patrick
Re: is(this : myClass)
On Friday, 20 October 2017 at 23:24:17 UTC, Patrick wrote:
On Friday, 20 October 2017 at 23:01:25 UTC, Steven
Schveighoffer wrote:
On 10/20/17 6:23 PM, Patrick wrote:
On Friday, 20 October 2017 at 22:15:36 UTC, Steven
Schveighoffer wrote:
On 10/20/17 5:55 PM, Patrick wrote:
Due to the very specific nature of the 'is' operator, why
wouldn't the compiler know to implicitly query the class
types? Why must it be explicitly written, typeof(this)?
The compiler generally doesn't "fix" errors for you, it
tells you there is a problem, and then you have to fix it.
You have to be clear and unambiguous to the compiler.
Otherwise debugging would be hell.
Not asking the compiler to fix my errors.
When would
is(this, myClass) not mean: is(typeof(this) :
typeof(myClass))?
class C
{
}
int c;
C myC;
is(myC : c);
oops, forgot to capitalize. But compiler says "I know, you
really meant is(typeof(myC) : typeof(c)) -> false.
-Steve
If I explicitly wrote: is(typeof(myC) : typeof(c)) the outcome
would still be false and it would still require debugging. So
your example demonstrates nothing other then a type-o was made.
Try again...
In this unique case, the compiler should identify the class and
primitive types are incompatible and should issue an error
instead (and not return false).
Patrick
But with the current compiler you would never write
is(typeOf(myC) : typeof(c))
if in your mind "c" is actually a class "C" because if that is in
your mind you would just write
is(typeof(myC) : c)
which would get you the error. You only need typeof(variable) to
get to the type, there is no point in doing typeof(type), you
just write type and C is a type. Right?
Re: is(this : myClass)
On Friday, 20 October 2017 at 23:01:25 UTC, Steven Schveighoffer
wrote:
On 10/20/17 6:23 PM, Patrick wrote:
On Friday, 20 October 2017 at 22:15:36 UTC, Steven
Schveighoffer wrote:
On 10/20/17 5:55 PM, Patrick wrote:
Due to the very specific nature of the 'is' operator, why
wouldn't the compiler know to implicitly query the class
types? Why must it be explicitly written, typeof(this)?
The compiler generally doesn't "fix" errors for you, it tells
you there is a problem, and then you have to fix it. You have
to be clear and unambiguous to the compiler. Otherwise
debugging would be hell.
Not asking the compiler to fix my errors.
When would
is(this, myClass) not mean: is(typeof(this) : typeof(myClass))?
class C
{
}
int c;
C myC;
is(myC : c);
oops, forgot to capitalize. But compiler says "I know, you
really meant is(typeof(myC) : typeof(c)) -> false.
-Steve
If I explicitly wrote: is(typeof(myC) : typeof(c)) the outcome
would still be false and it would still require debugging. So
your example demonstrates nothing other then a type-o was made.
Try again...
In this unique case, the compiler should identify the class and
primitive types are incompatible and should issue an error
instead (and not return false).
Patrick
Re: is(this : myClass)
On 10/20/17 7:04 PM, user1234 wrote:
Strangely this is not always true, in other contexts this is seen as
atype, although probably a bug
class Foo
{
class Bar : this {}
static assert(is(Bar : Foo));
}
Definitely a bug. You should have to write typeof(this) (which is valid
in this context).
-Steve
Re: is(this : myClass)
On 10/20/17 6:23 PM, Patrick wrote:
On Friday, 20 October 2017 at 22:15:36 UTC, Steven Schveighoffer wrote:
On 10/20/17 5:55 PM, Patrick wrote:
Due to the very specific nature of the 'is' operator, why wouldn't
the compiler know to implicitly query the class types? Why must it be
explicitly written, typeof(this)?
The compiler generally doesn't "fix" errors for you, it tells you
there is a problem, and then you have to fix it. You have to be clear
and unambiguous to the compiler. Otherwise debugging would be hell.
Not asking the compiler to fix my errors.
When would
is(this, myClass) not mean: is(typeof(this) : typeof(myClass))?
class C
{
}
int c;
C myC;
is(myC : c);
oops, forgot to capitalize. But compiler says "I know, you really meant
is(typeof(myC) : typeof(c)) -> false.
-Steve
Re: is(this : myClass)
On Friday, 20 October 2017 at 21:42:32 UTC, Jonathan M Davis
wrote:
On Friday, October 20, 2017 21:32:48 Patrick via
Digitalmars-d-learn wrote:
The compiler seems to reject the following code in a class
method:
bool test = is(this : myClass);
Could some please explain this?
"this" is not a type.
Strangely this is not always true, in other contexts this is seen
as atype, although probably a bug
class Foo
{
class Bar : this {}
static assert(is(Bar : Foo));
}
Re: is(this : myClass)
On Friday, 20 October 2017 at 22:15:36 UTC, Steven Schveighoffer wrote: On 10/20/17 5:55 PM, Patrick wrote: Due to the very specific nature of the 'is' operator, why wouldn't the compiler know to implicitly query the class types? Why must it be explicitly written, typeof(this)? The compiler generally doesn't "fix" errors for you, it tells you there is a problem, and then you have to fix it. You have to be clear and unambiguous to the compiler. Otherwise debugging would be hell. -Steve Not asking the compiler to fix my errors. When would is(this, myClass) not mean: is(typeof(this) : typeof(myClass))? Why would "is(this, myClass)" be ambiguous? What other interpretation would "is(this, myClass)" imply? Patrick
Re: is(this : myClass)
On 10/20/17 5:55 PM, Patrick wrote: Due to the very specific nature of the 'is' operator, why wouldn't the compiler know to implicitly query the class types? Why must it be explicitly written, typeof(this)? The compiler generally doesn't "fix" errors for you, it tells you there is a problem, and then you have to fix it. You have to be clear and unambiguous to the compiler. Otherwise debugging would be hell. -Steve
Re: is(this : myClass)
On Friday, 20 October 2017 at 21:42:32 UTC, Jonathan M Davis wrote: On Friday, October 20, 2017 21:32:48 Patrick via Digitalmars-d-learn wrote: The compiler seems to reject the following code in a class method: bool test = is(this : myClass); Could some please explain this? "this" is not a type. is(T : U) is true if T is implicitly convertible to U. T and U must both be types. So, you need to use the types of this and myClass, even if that's just is(typeof(this) : typeof(myClass)) rather than explicitly using their types. - Jonathan M Davis Thank you. Due to the very specific nature of the 'is' operator, why wouldn't the compiler know to implicitly query the class types? Why must it be explicitly written, typeof(this)? Patrick
Re: is(this : myClass)
On Friday, October 20, 2017 21:32:48 Patrick via Digitalmars-d-learn wrote: > The compiler seems to reject the following code in a class method: > > bool test = is(this : myClass); > > Could some please explain this? "this" is not a type. is(T : U) is true if T is implicitly convertible to U. T and U must both be types. So, you need to use the types of this and myClass, even if that's just is(typeof(this) : typeof(myClass)) rather than explicitly using their types. - Jonathan M Davis
is(this : myClass)
The compiler seems to reject the following code in a class method: bool test = is(this : myClass); Could some please explain this? Thanks, Patrick
