throws Exception in method
Hello everyone,
in java, you can have exceptions on methods.
Thus we can write:
public static void control (String string) throws
MyException {}
Is that possible in D and if so how does it work? If I write this
D:
public void testMe () throws MyException {}
The compiler refuses to compile.
What is the proper behavior for this D?
thank you
Re: throws Exception in method
On Thursday, 8 May 2014 at 09:15:16 UTC, amehat wrote:
Hello everyone,
in java, you can have exceptions on methods.
Thus we can write:
public static void control (String string) throws
MyException {}
Is that possible in D and if so how does it work? If I write
this D:
public void testMe () throws MyException {}
The compiler refuses to compile.
What is the proper behavior for this D?
thank you
All functions/methods can throw in D, unless they are marked
nothrow.
Re: throws Exception in method
amehat: What is the proper behavior for this D? D doesn't have that Java syntax, because it was widely regarded as a Java design mistake. So in D omit the throws part. If your function tree doesn't throw exceptions (but it can throw errors) add a nothrow. Bye, bearophile
Re: throws Exception in method
On Thu, 08 May 2014 09:15:13 +
amehat via Digitalmars-d-learn digitalmars-d-learn@puremagic.com
wrote:
Hello everyone,
in java, you can have exceptions on methods.
Thus we can write:
public static void control (String string) throws
MyException {}
Is that possible in D and if so how does it work? If I write this
D:
public void testMe () throws MyException {}
The compiler refuses to compile.
What is the proper behavior for this D?
thank you
At this point, the programming community at large seems to have decided that
while checked exceptions seem like a good idea, they're ultimately a bad one.
This article has a good explanation from one of the creators of C# as to why:
http://www.artima.com/intv/handcuffs.html
At this point, Java is the only language I'm aware of which has checked
exceptions (though there may be a few others somewhere), and newer languages
have learned from Java's mistake and chosen not to have them.
What D has instead is the attribute nothrow. Any function marked with nothrow
cannot throw an exception. e.g.
auto func(int bar) nothrow {...}
It's similar to C++11's noexcept except that it's checked at compile time
(like Java's checked exceptions), whereas noexcept introduces a runtime check.
If a function is not marked with nothrow, then the only ways to know what it
can throw are to read the documentation (which may or may not say) or to read
the code. There are obviously downsides to that in comparison to checked
exceptions, but the consensus at this point is that it's ultimately better.
- Jonathan M Davis
Re: throws Exception in method
On Thursday, 8 May 2014 at 10:14:27 UTC, Jonathan M Davis via
Digitalmars-d-learn wrote:
On Thu, 08 May 2014 09:15:13 +
amehat via Digitalmars-d-learn
digitalmars-d-learn@puremagic.com
wrote:
Hello everyone,
in java, you can have exceptions on methods.
Thus we can write:
public static void control (String string) throws
MyException {}
Is that possible in D and if so how does it work? If I write
this
D:
public void testMe () throws MyException {}
The compiler refuses to compile.
What is the proper behavior for this D?
thank you
At this point, the programming community at large seems to have
decided that
while checked exceptions seem like a good idea, they're
ultimately a bad one.
This article has a good explanation from one of the creators of
C# as to why:
http://www.artima.com/intv/handcuffs.html
At this point, Java is the only language I'm aware of which has
checked
exceptions (though there may be a few others somewhere), and
newer languages
have learned from Java's mistake and chosen not to have them.
What D has instead is the attribute nothrow. Any function
marked with nothrow
cannot throw an exception. e.g.
auto func(int bar) nothrow {...}
It's similar to C++11's noexcept except that it's checked at
compile time
(like Java's checked exceptions), whereas noexcept introduces a
runtime check.
If a function is not marked with nothrow, then the only ways to
know what it
can throw are to read the documentation (which may or may not
say) or to read
the code. There are obviously downsides to that in comparison
to checked
exceptions, but the consensus at this point is that it's
ultimately better.
- Jonathan M Davis
My English might not be very good and I'm not sure I understand.
If I understand what you say, D for all methods (and functions)
can raise exceptions, unless it has nothrow. And if I still
includes exceptions that are thrown are at the time of
compilation.
So I can not write:
public void testMe () throws MyException {}
However, if I write this and my method throws an exception, it
will take place at compile time:
public void testMe () {}
And if do not want an exception thrown, I should write:
public void testMe () : nothrow {}
or perhaps :
public void testMe () pure nothrow @safe {}
Is that correct?
PS: Thanks for the article on the interveiw Anders Hejlsberg, it
enlightens me a little more about how exceptions sen D (and C #;))
Re: throws Exception in method
On Thursday, 8 May 2014 at 12:00:40 UTC, amehat wrote:
On Thursday, 8 May 2014 at 10:14:27 UTC, Jonathan M Davis via
Digitalmars-d-learn wrote:
On Thu, 08 May 2014 09:15:13 +
amehat via Digitalmars-d-learn
digitalmars-d-learn@puremagic.com
wrote:
Hello everyone,
in java, you can have exceptions on methods.
Thus we can write:
public static void control (String string) throws
MyException {}
Is that possible in D and if so how does it work? If I write
this
D:
public void testMe () throws MyException {}
The compiler refuses to compile.
What is the proper behavior for this D?
thank you
At this point, the programming community at large seems to
have decided that
while checked exceptions seem like a good idea, they're
ultimately a bad one.
This article has a good explanation from one of the creators
of C# as to why:
http://www.artima.com/intv/handcuffs.html
At this point, Java is the only language I'm aware of which
has checked
exceptions (though there may be a few others somewhere), and
newer languages
have learned from Java's mistake and chosen not to have them.
What D has instead is the attribute nothrow. Any function
marked with nothrow
cannot throw an exception. e.g.
auto func(int bar) nothrow {...}
It's similar to C++11's noexcept except that it's checked at
compile time
(like Java's checked exceptions), whereas noexcept introduces
a runtime check.
If a function is not marked with nothrow, then the only ways
to know what it
can throw are to read the documentation (which may or may not
say) or to read
the code. There are obviously downsides to that in comparison
to checked
exceptions, but the consensus at this point is that it's
ultimately better.
- Jonathan M Davis
My English might not be very good and I'm not sure I understand.
If I understand what you say, D for all methods (and functions)
can raise exceptions, unless it has nothrow. And if I still
includes exceptions that are thrown are at the time of
compilation.
So I can not write:
public void testMe () throws MyException {}
However, if I write this and my method throws an exception, it
will take place at compile time:
public void testMe () {}
And if do not want an exception thrown, I should write:
public void testMe () : nothrow {}
or perhaps :
public void testMe () pure nothrow @safe {}
Is that correct?
PS: Thanks for the article on the interveiw Anders Hejlsberg,
it enlightens me a little more about how exceptions sen D (and
C #;))
Exceptions are runtime-only (or ctfe (compile time function
execution), but that's not relevant here).
functions that are not marked nothrow can, at any point in the
body of the function, exit via an exception. Functions marked
nothrow cannot exit via an exception; the compiler must be able
to prove that all exceptions that could be thrown are caught, e.g.
void foo() nothrow
{
try
{
throw new Exception();
}
catch(Exception e){}
}
is fine.
Re: throws Exception in method
On Thursday, 8 May 2014 at 12:27:55 UTC, John Colvin wrote:
On Thursday, 8 May 2014 at 12:00:40 UTC, amehat wrote:
On Thursday, 8 May 2014 at 10:14:27 UTC, Jonathan M Davis via
Digitalmars-d-learn wrote:
On Thu, 08 May 2014 09:15:13 +
amehat via Digitalmars-d-learn
digitalmars-d-learn@puremagic.com
wrote:
Hello everyone,
in java, you can have exceptions on methods.
Thus we can write:
public static void control (String string) throws
MyException {}
Is that possible in D and if so how does it work? If I write
this
D:
public void testMe () throws MyException {}
The compiler refuses to compile.
What is the proper behavior for this D?
thank you
At this point, the programming community at large seems to
have decided that
while checked exceptions seem like a good idea, they're
ultimately a bad one.
This article has a good explanation from one of the creators
of C# as to why:
http://www.artima.com/intv/handcuffs.html
At this point, Java is the only language I'm aware of which
has checked
exceptions (though there may be a few others somewhere), and
newer languages
have learned from Java's mistake and chosen not to have them.
What D has instead is the attribute nothrow. Any function
marked with nothrow
cannot throw an exception. e.g.
auto func(int bar) nothrow {...}
It's similar to C++11's noexcept except that it's checked at
compile time
(like Java's checked exceptions), whereas noexcept introduces
a runtime check.
If a function is not marked with nothrow, then the only ways
to know what it
can throw are to read the documentation (which may or may not
say) or to read
the code. There are obviously downsides to that in comparison
to checked
exceptions, but the consensus at this point is that it's
ultimately better.
- Jonathan M Davis
My English might not be very good and I'm not sure I
understand.
If I understand what you say, D for all methods (and
functions) can raise exceptions, unless it has nothrow. And if
I still includes exceptions that are thrown are at the time of
compilation.
So I can not write:
public void testMe () throws MyException {}
However, if I write this and my method throws an exception, it
will take place at compile time:
public void testMe () {}
And if do not want an exception thrown, I should write:
public void testMe () : nothrow {}
or perhaps :
public void testMe () pure nothrow @safe {}
Is that correct?
PS: Thanks for the article on the interveiw Anders Hejlsberg,
it enlightens me a little more about how exceptions sen D (and
C #;))
Exceptions are runtime-only (or ctfe (compile time function
execution), but that's not relevant here).
functions that are not marked nothrow can, at any point in the
body of the function, exit via an exception. Functions marked
nothrow cannot exit via an exception; the compiler must be able
to prove that all exceptions that could be thrown are caught,
e.g.
void foo() nothrow
{
try
{
throw new Exception();
}
catch(Exception e){}
}
is fine.
Okay.
Thank you for these explanations, I understand a little better
the exceptions D.
Re: throws Exception in method
On Thursday, 8 May 2014 at 13:06:05 UTC, amehat wrote: Okay. Thank you for these explanations, I understand a little better the exceptions D. Keep in mind that D also has the concept of Error. Both Exception and Error derive from Throwable. nothrow only means the function will not throw an *Exception*. Error can be thrown any time, from anywhere. They bypass the nothrow, bypass destructor cleanup, and fly past catch (Exception). An Error is basically: A critical Error has occurred. Salvage what you can before dying.
Re: throws Exception in method
On Thursday, 8 May 2014 at 14:02:06 UTC, monarch_dodra wrote: On Thursday, 8 May 2014 at 13:06:05 UTC, amehat wrote: Okay. Thank you for these explanations, I understand a little better the exceptions D. Keep in mind that D also has the concept of Error. Both Exception and Error derive from Throwable. nothrow only means the function will not throw an *Exception*. Error can be thrown any time, from anywhere. They bypass the nothrow, bypass destructor cleanup, and fly past catch (Exception). An Error is basically: A critical Error has occurred. Salvage what you can before dying. I do not know the mistakes, at least not as you speak. I just read on http://dlang.org/errors.html errors. You mean errors and exceptions are almost identical?
Re: throws Exception in method
On Thu, May 08, 2014 at 03:19:04PM +, amehat via Digitalmars-d-learn wrote: On Thursday, 8 May 2014 at 14:02:06 UTC, monarch_dodra wrote: [...] Keep in mind that D also has the concept of Error. Both Exception and Error derive from Throwable. nothrow only means the function will not throw an *Exception*. Error can be thrown any time, from anywhere. They bypass the nothrow, bypass destructor cleanup, and fly past catch (Exception). An Error is basically: A critical Error has occurred. Salvage what you can before dying. I do not know the mistakes, at least not as you speak. I just read on http://dlang.org/errors.html errors. You mean errors and exceptions are almost identical? What he meant, is that in D there are two kinds of throwables: Throwable /\ Exception Errors The 'nothrow' attribute means that the function will not throw an Exception. But it does not guarantee that it will not throw something else, like an AssertError (which is a subclass of Throwable but not a subclass of Exception). The intention is that normal exceptions must all inherit from class Exception. Exceptions represent recoverable problems that can be handled by catch blocks. Other Throwable subclasses, like Errors, represent non-recoverable problems with the program. E.g., AssertError means a wrong logic in the program was detected by an assert statement, so the program is in an inconsistent state that cannot be recovered from. So you should never catch an Error. Or if ever you do, you should make sure you terminate the program immediately afterwards. Also, note that some language guarantees will not hold when inside an Error catch block, so it's a bad idea to do anything other than emergency cleanup and then terminate the program. T -- Genius may have its limitations, but stupidity is not thus handicapped. -- Elbert Hubbard
