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digitalmars.D - What does 'final' keyword exactly?

reply "Andrew Fedoniouk" <news terrainformatica.com> writes:
E.g. here: (std.openrj)

class Field
{
....
    final char[]  name()
    {
        return m_name;
    }
    final char[]  value()
    {
        return m_value;
    }
...
}

Andrew.
Jun 05 2005
next sibling parent reply "Jarrett Billingsley" <kb3ctd2 yahoo.com> writes:
"Andrew Fedoniouk" <news terrainformatica.com> wrote in message 
news:d8081t$2bba$1 digitaldaemon.com...

 class Field
 {
 ....
    final char[]  name()
    {
        return m_name;
    }
    final char[]  value()
    {
        return m_value;
    }
 ...
 }


Makes it so you can't override that function in derived classes.

In other languages (I think C++ and Java, though it's called "sealed" in one 
of them), when applied to a class, it means the class can't be derived from. 
But that doesn't work in D.
Jun 05 2005
next sibling parent "Jarrett Billingsley" <kb3ctd2 yahoo.com> writes:
"Jarrett Billingsley" <kb3ctd2 yahoo.com> wrote in message 
news:d80akp$2cqh$1 digitaldaemon.com...


 In other languages (I think C++ and Java, though it's called "sealed" in 
 one of them), when applied to a class, it means the class can't be derived 
 from. But that doesn't work in D.
Jun 05 2005
prev sibling next sibling parent "Andrew Fedoniouk" <news terrainformatica.com> writes:
"Jarrett Billingsley" <kb3ctd2 yahoo.com> wrote in message 
news:d80akp$2cqh$1 digitaldaemon.com...

 "Andrew Fedoniouk" <news terrainformatica.com> wrote in message 
 news:d8081t$2bba$1 digitaldaemon.com...

 class Field
 {
 ....
    final char[]  name()
    {
        return m_name;
    }
    final char[]  value()
    {
        return m_value;
    }
 ...
 }


 Makes it so you can't override that function in derived classes.

 In other languages (I think C++ and Java, though it's called "sealed" in 
 one of them), when applied to a class, it means the class can't be derived 
 from. But that doesn't work in D.


Yep. Thanks. That is in Java.

Next question is what are the desing goals of
having two final functions and left 'record'
non-final?
(std.openrj)
class Field
{
    final char[]  name() {       return m_name;    }
    final char[]  value() {       return m_value;    }
    Record       record() {    return m_record;   }
}

For me it seems that Matthew was trying to use final
as a const for returning char[].

Andrew.
Jun 05 2005
prev sibling parent reply "Andrew Fedoniouk" <news terrainformatica.com> writes:
final [snip]

 when applied to a class, it means the class can't be derived from. But 
 that doesn't work in D.


Found answer:

Sat, 23 Aug 2003 10:23:29 -0700 "Walter" <walter xx digitalmars.com> writes:

Looks like a compiler bug.

"Carlos Santander B." <carlos8294 xx msn.com> wrote in message
news:bi65mo$2a9n$1 xx digitaldaemon.com...

 What's the purpose of 'final' in D?
 This code compiles just fine:
 final class A {}
 class B:A { }
 void main() {
 B b=new B();
 }

 -------------------------
 Carlos Santander


http://www.digitalmars.com/d/archives/16022.html
Jun 05 2005
parent "Jarrett Billingsley" <kb3ctd2 yahoo.com> writes:
"Andrew Fedoniouk" <news terrainformatica.com> wrote in message 
news:d80eg3$2fh0$1 digitaldaemon.com...

 final [snip]

 when applied to a class, it means the class can't be derived from. But 
 that doesn't work in D.


 Found answer:

 Sat, 23 Aug 2003 10:23:29 -0700 "Walter" <walter xx digitalmars.com> 
 writes:

 Looks like a compiler bug.


Ooh goody!  Which means that it _will_ work like that :)
Jun 06 2005
prev sibling parent reply Derek Parnell <derek psych.ward> writes:
On Sun, 5 Jun 2005 18:14:33 -0700, Andrew Fedoniouk wrote:


 E.g. here: (std.openrj)
 
 class Field
 {
 ....
     final char[]  name()
     {
         return m_name;
     }
     final char[]  value()
     {
         return m_value;
     }
 ...
 }
 
 Andrew.


My understanding is that you can't derive  a new class from this class
*and* override any of the 'final' members. That is, you can't do this sort
of thing ...

class Field
{
    char[] m_name;
    char[] m_value;

    final char[]  name()
    {
        return m_name;
    }
    final char[]  value()
    {
        return m_value;
    }

}

class SField : Field
{
    char[] mx_name;
    char[] mx_value;
    char[] name()  // Fails.
    {
        return mx_name;
    }

}


-- 
Derek
Melbourne, Australia
6/06/2005 12:02:05 PM
Jun 05 2005
parent reply "Andrew Fedoniouk" <news terrainformatica.com> writes:
"Derek Parnell" <derek psych.ward> wrote in message 
news:leailo4fvus.m2wubh7asozc.dlg 40tude.net...

 On Sun, 5 Jun 2005 18:14:33 -0700, Andrew Fedoniouk wrote:


 E.g. here: (std.openrj)

 class Field
 {
 ....
     final char[]  name()
     {
         return m_name;
     }
     final char[]  value()
     {
         return m_value;
     }
 ...
 }

 Andrew.


 My understanding is that you can't derive  a new class from this class
 *and* override any of the 'final' members. That is, you can't do this sort
 of thing ...


[snip]

Thanks, Derek,
I know what 'final' does in Java. But what it does in D?
Asking because 'final' is not defined in documentation.
At least I didn't find it.

In fact 'final' in Java does many things, I would say too many.
http://www.codeguru.com/java/tij/tij0071.shtml

Andrew.
Jun 05 2005
parent reply Derek Parnell <derek psych.ward> writes:
On Sun, 5 Jun 2005 19:39:40 -0700, Andrew Fedoniouk wrote:


 "Derek Parnell" <derek psych.ward> wrote in message 
 news:leailo4fvus.m2wubh7asozc.dlg 40tude.net...

 On Sun, 5 Jun 2005 18:14:33 -0700, Andrew Fedoniouk wrote:


 E.g. here: (std.openrj)

 class Field
 {
 ....
     final char[]  name()
     {
         return m_name;
     }
     final char[]  value()
     {
         return m_value;
     }
 ...
 }

 Andrew.


 My understanding is that you can't derive  a new class from this class
 *and* override any of the 'final' members. That is, you can't do this sort
 of thing ...


 
 [snip]
 
 Thanks, Derek,
 I know what 'final' does in Java. But what it does in D?


I don't know Java. I *told* you what is does in D. I wrote a test program
and tried it out before replying to your post.


 Asking because 'final' is not defined in documentation.
 At least I didn't find it.


I agree; its meaning is not documented.


 In fact 'final' in Java does many things, I would say too many.


Whatever ... I just looked at what it does in D - to answer your original
question with respect to the code sample you gave.

-- 
Derek
Melbourne, Australia
6/06/2005 1:21:14 PM
Jun 05 2005
parent "Andrew Fedoniouk" <news terrainformatica.com> writes:
"Derek Parnell" <derek psych.ward> wrote in message 
news:ozn0oihlm1z6$.mcz62ecxpoz4$.dlg 40tude.net...

 On Sun, 5 Jun 2005 19:39:40 -0700, Andrew Fedoniouk wrote:


 "Derek Parnell" <derek psych.ward> wrote in message
 news:leailo4fvus.m2wubh7asozc.dlg 40tude.net...

 On Sun, 5 Jun 2005 18:14:33 -0700, Andrew Fedoniouk wrote:


 E.g. here: (std.openrj)

 class Field
 {
 ....
     final char[]  name()
     {
         return m_name;
     }
     final char[]  value()
     {
         return m_value;
     }
 ...
 }

 Andrew.


 My understanding is that you can't derive  a new class from this class
 *and* override any of the 'final' members. That is, you can't do this 
 sort
 of thing ...


 [snip]

 Thanks, Derek,
 I know what 'final' does in Java. But what it does in D?


 I don't know Java. I *told* you what is does in D. I wrote a test program
 and tried it out before replying to your post.


 Asking because 'final' is not defined in documentation.
 At least I didn't find it.


 I agree; its meaning is not documented.


 In fact 'final' in Java does many things, I would say too many.


 Whatever ... I just looked at what it does in D - to answer your original
 question with respect to the code sample you gave.


Derek, no offence was implied from my side.
I simply did not get what 'final' is doing in code fragment I provided
from openrj. For me it seems like remnants of previous desicisions/
implementations. That is why I asked. Again no claims of any sort.

Andrew.
Jun 05 2005