digitalmars.D.learn - Two question about array

Alex (5/5) Dec 30 2007 1. Is array a class derived from Object? If yes, why i get error message...

Derek Parnell (35/40) Dec 30 2007 Have a look at the std.boxer module, that might be what you are looking

Jarrett Billingsley (3/3) Dec 30 2007 "Derek Parnell" wrote in message

Jarrett Billingsley (14/23) Dec 30 2007 Arrays are not objects. They are arrays :) They are their own type and...

Alex (21/51) Dec 31 2007 I'm trying to use Variant but got error message with the following code:

Jarrett Billingsley (6/28) Dec 31 2007 I've never used Phobos' std.variant, but it looks like a typical issue w...
Derek Parnell (24/48) Dec 31 2007 Which version of the DMD comiler are you using?

Alex (3/61) Dec 31 2007 The error occured with dmd 2.007.

Jarrett Billingsley (6/12) Dec 31 2007 That would be the change log. The newest version is always at the top o...

Alex <faint_u 163.com> writes:

1. Is array a class derived from Object? If yes, why i get error message with
the following code:
	int[] array;
	Object obj = array;
If not, is there any general type can represent either an Integer, or an Array?
Or a character string?

2. simpleArray.length = simpleArray.length * 2 can pass the compile but
simpleArray.length *= 2 can't. The compiler complains "simpleArray.length is
not an lvalue", what's the problem?

Dec 30 2007

Derek Parnell <derek psych.ward> writes:

On Sun, 30 Dec 2007 09:09:37 -0500, Alex wrote:

 1. Is array a class derived from Object? If yes, why i get error message with
the following code:
 	int[] array;
 	Object obj = array;

No, an array is not a class.

 If not, is there any general type can represent either an Integer, or an
Array? Or a character string?

Have a look at the std.boxer module, that might be what you are looking
for. 

 2. simpleArray.length = simpleArray.length * 2 can pass the compile but
simpleArray.length *= 2 can't. The compiler complains "simpleArray.length is
not an lvalue", what's the problem?

This is a current restriction in D.

The reason is that the .length is a property (albeit a built-in one) and
properties are implemented as function calls. This means that ...

    simpleArray.length *= 2

is equivalent to ...

    get_length(simpleArray) *= 2

which as you can imagine is not going to do what you want. Whereas ...

   simpleArray.length = simpleArray.length * 2

is equivalent to ...

   set_length(simpleArray, get_length(simpleArray) * 2 )

Hopefully, this is one of the restrictions that can be removed soon.

This restriction applies to user defined properties too.

For example:

class Foo
{
    float m_Value  = 0;

    int  val()       { return cast(int)m_Value; }
    void val( int x) { m_Value = cast(float)x); }
}

 Foo f = new Foo;

 int a;

 a = f.val; // okay
 a += 2;
 f.val = a; // okay;

 f.val += 2; // Not okay.


 

  


-- 
Derek Parnell
Melbourne, Australia
skype: derek.j.parnell

Dec 30 2007

"Jarrett Billingsley" <kb3ctd2 yahoo.com> writes:

"Derek Parnell" <derek psych.ward> wrote in message 
news:7zy1pvtteo79$.1ligslws4mjpl.dlg 40tude.net...

RRRRRRGH TIE

Dec 30 2007

"Jarrett Billingsley" <kb3ctd2 yahoo.com> writes:

"Alex" <faint_u 163.com> wrote in message 
news:fl88r1$1olc$1 digitalmars.com...
 1. Is array a class derived from Object? If yes, why i get error message 
 with the following code:
 int[] array;
 Object obj = array;
 If not, is there any general type can represent either an Integer, or an 
 Array? Or a character string?

Arrays are not objects.  They are arrays :)  They are their own type and are 
not related to any other type.

If you need an integer or an array you need some kind of variant type.  If 
you're using Tango, there's tango.core.Variant; if you're using Phobos with 
D1, there's std.boxer; and Phobos with D2 has deprecated std.boxer in favor 
of std.variant.

 2. simpleArray.length = simpleArray.length * 2 can pass the compile but 
 simpleArray.length *= 2 can't. The compiler complains "simpleArray.length 
 is not an lvalue", what's the problem?

It's because these are really syntactic sugar for function calls. 
"simpleArray.length = 5" is the same as "simpleArray.length(5)".  If you try 
to do "simpleArray.length *= 2" you're basically writing 
"simpleArray.length() *= 2", which obviously makes no sense.  The same thing 
would happen with class properties.

It's dumb.  I know.

Dec 30 2007

Alex <faint_u 163.com> writes:

I'm trying to use Variant but got error message with the following code:
-------------------------------------------
import std.variant;

void main()
{
	Variant v;
	v = 4;
}

-----------------------------
error message:

E:\Tools\Lang\D>dmd test.d
e:\Tools\Lang\d\dmd\bin\..\..\dm\bin\link.exe test,,,user32+kernel32/noi;
OPTLINK (R) for Win32  Release 8.00.1
Copyright (C) Digital Mars 1989-2004  All rights reserved.
test.obj(test)
 Error 42: Symbol Undefined
_D3std7variant17__T8VariantNVk20Z8VariantN4typeMFZC8TypeInfo
test.obj(test)
 Error 42: Symbol Undefined _D3std7variant17__T8VariantNVk20Z8VariantN6__initZ
--- errorlevel 2

What's the problem?

Jarrett Billingsley Wrote:

 "Alex" <faint_u 163.com> wrote in message 
 news:fl88r1$1olc$1 digitalmars.com...
 1. Is array a class derived from Object? If yes, why i get error message 
 with the following code:
 int[] array;
 Object obj = array;
 If not, is there any general type can represent either an Integer, or an 
 Array? Or a character string?

 
 Arrays are not objects.  They are arrays :)  They are their own type and are 
 not related to any other type.
 
 If you need an integer or an array you need some kind of variant type.  If 
 you're using Tango, there's tango.core.Variant; if you're using Phobos with 
 D1, there's std.boxer; and Phobos with D2 has deprecated std.boxer in favor 
 of std.variant.
 
 2. simpleArray.length = simpleArray.length * 2 can pass the compile but 
 simpleArray.length *= 2 can't. The compiler complains "simpleArray.length 
 is not an lvalue", what's the problem?

 
 It's because these are really syntactic sugar for function calls. 
 "simpleArray.length = 5" is the same as "simpleArray.length(5)".  If you try 
 to do "simpleArray.length *= 2" you're basically writing 
 "simpleArray.length() *= 2", which obviously makes no sense.  The same thing 
 would happen with class properties.
 
 It's dumb.  I know.

Dec 31 2007

"Jarrett Billingsley" <kb3ctd2 yahoo.com> writes:

"Alex" <faint_u 163.com> wrote in message 
news:flaqh4$14v7$1 digitalmars.com...
 I'm trying to use Variant but got error message with the following code:
 -------------------------------------------
 import std.variant;

 void main()
 {
 Variant v;
 v = 4;
 }

 -----------------------------
 error message:

 E:\Tools\Lang\D>dmd test.d
 e:\Tools\Lang\d\dmd\bin\..\..\dm\bin\link.exe test,,,user32+kernel32/noi;
 OPTLINK (R) for Win32  Release 8.00.1
 Copyright (C) Digital Mars 1989-2004  All rights reserved.
 test.obj(test)
 Error 42: Symbol Undefined 
 _D3std7variant17__T8VariantNVk20Z8VariantN4typeMFZC8TypeInfo
 test.obj(test)
 Error 42: Symbol Undefined 
 _D3std7variant17__T8VariantNVk20Z8VariantN6__initZ
 --- errorlevel 2

 What's the problem?

I've never used Phobos' std.variant, but it looks like a typical issue with 
DMD, OPTLINK, precompiled libraries and templates (that is, DMD+OPTLINK 
usually fall flat on their face when trying to use templates from a library 
that's been precompiled).  I don't know how to make it work :\

Dec 31 2007

Derek Parnell <derek psych.ward> writes:

On Mon, 31 Dec 2007 08:23:48 -0500, Alex wrote:

 I'm trying to use Variant but got error message with the following code:
 -------------------------------------------
 import std.variant;
 
 void main()
 {
 	Variant v;
 	v = 4;
 }
 
 -----------------------------
 error message:
 
 E:\Tools\Lang\D>dmd test.d
 e:\Tools\Lang\d\dmd\bin\..\..\dm\bin\link.exe test,,,user32+kernel32/noi;
 OPTLINK (R) for Win32  Release 8.00.1
 Copyright (C) Digital Mars 1989-2004  All rights reserved.
 test.obj(test)
  Error 42: Symbol Undefined
_D3std7variant17__T8VariantNVk20Z8VariantN4typeMFZC8TypeInfo
 test.obj(test)
  Error 42: Symbol Undefined _D3std7variant17__T8VariantNVk20Z8VariantN6__initZ
 --- errorlevel 2
 
 What's the problem?

Which version of the DMD comiler are you using?

When I tried your example with version 2.008 it worked...

---------------
C:\temp>type test.d
import std.stdio;
import std.variant;

void main()
{
        Variant v;
        v = 4;

        writefln("%s", v);
}
C:\temp>dmd test.d
c:\dmd\dmd\bin\..\..\dm\bin\link.exe test,,,user32+kernel32/noi;

C:\temp>test
4

C:\temp>dmd
Digital Mars D Compiler v2.008

----------------

-- 
Derek Parnell
Melbourne, Australia
skype: derek.j.parnell

Dec 31 2007

Alex <faint_u 163.com> writes:

The error occured with dmd 2.007. 
I just tried 2.008 and it works now. BTW, where is the download page for latest
dmd compiler? The one in page http://www.digitalmars.com/d/dcompiler.html is
still version 2.007. I replaced the 2.007 to 2.008 in the URL to get the
correct version. But i think there should be a web page always listing the
latest version.

Derek Parnell Wrote:

 On Mon, 31 Dec 2007 08:23:48 -0500, Alex wrote:
 
 I'm trying to use Variant but got error message with the following code:
 -------------------------------------------
 import std.variant;
 
 void main()
 {
 	Variant v;
 	v = 4;
 }
 
 -----------------------------
 error message:
 
 E:\Tools\Lang\D>dmd test.d
 e:\Tools\Lang\d\dmd\bin\..\..\dm\bin\link.exe test,,,user32+kernel32/noi;
 OPTLINK (R) for Win32  Release 8.00.1
 Copyright (C) Digital Mars 1989-2004  All rights reserved.
 test.obj(test)
  Error 42: Symbol Undefined
_D3std7variant17__T8VariantNVk20Z8VariantN4typeMFZC8TypeInfo
 test.obj(test)
  Error 42: Symbol Undefined _D3std7variant17__T8VariantNVk20Z8VariantN6__initZ
 --- errorlevel 2
 
 What's the problem?

 
 Which version of the DMD comiler are you using?
 
 When I tried your example with version 2.008 it worked...
 
 ---------------
 C:\temp>type test.d
 import std.stdio;
 import std.variant;
 
 void main()
 {
         Variant v;
         v = 4;
 
         writefln("%s", v);
 }
 C:\temp>dmd test.d
 c:\dmd\dmd\bin\..\..\dm\bin\link.exe test,,,user32+kernel32/noi;
 
 C:\temp>test
 4
 
 C:\temp>dmd
 Digital Mars D Compiler v2.008
 
 ----------------
 
 -- 
 Derek Parnell
 Melbourne, Australia
 skype: derek.j.parnell

Dec 31 2007

"Jarrett Billingsley" <kb3ctd2 yahoo.com> writes:

"Alex" <faint_u 163.com> wrote in message 
news:flb58s$1r2o$1 digitalmars.com...
 The error occured with dmd 2.007.
 I just tried 2.008 and it works now. BTW, where is the download page for 
 latest dmd compiler? The one in page 
 http://www.digitalmars.com/d/dcompiler.html is still version 2.007. I 
 replaced the 2.007 to 2.008 in the URL to get the correct version. But i 
 think there should be a web page always listing the latest version.

That would be the change log.  The newest version is always at the top of 
the changelog; click on the version number to get the latest version.

I really wish Walter would stop putting older versions as "stable" versions 
because they never seem to be as good as the newest ones :P

Dec 31 2007

D Programming

C/C++ Programming

Other

digitalmars.D.learn - Two question about array