Let us admire this partial code,

class User
{
char [] userID = null;
char [] fname = null;
char [] lname = null;
char [] NameOut  = null;
FCount forms[] = null;
}
class FCount
{
char[] FormApp = "Language";
int    FormCnt = 0;
}
User ProcessUserForms(char[] fxml, User u)
{
int i = 0;
bit found = false;
char[][] t;
t = std.string.split(fxml,"<Application name=\"");
t = std.string.split(t[1],".Applicat");
t = std.string.split(t[0],"applications.");
if(u.forms == null) //.length < 1)
{
FCount fc = new FCount();
u.forms.length = 1;
u.forms[0] = fc;
u.forms[0].FormApp = t[1];
u.forms[0].FormCnt = 1;
found = true;
}
else
{
for(i=0; i < u.forms.length; i++)
{
if(std.string.cmp(u.forms[i].FormApp,t[1]) == 0)
{
found = true;
u.forms[i].FormCnt++;
break;
}
}
if(!found)
{
FCount fc = new FCount();
u.forms.length = u.forms.length + 1; // observe this line
u.forms[length - 1] = fc;
u.forms[length - 1].FormApp = t[1];
u.forms[length - 1].FormCnt = 1;
}
}
return u;
}

This code compiles perfecty, but if I change this line

u.forms.length = u.forms.length + 1; // observe this line

almost at the end, to

u.forms.length += 1; // observe this line

the compiler fails with

16:03:50.47>dmd DTSP1.d ws2_32.lib
DTSP1.d(740): u.forms.length is not an lvalue

Also, the same happens to,

u.forms.length++;

I just want to understand why.

thanks.

josé

The array length is considered a property of an array and so is consistent with properties as described under 'Class and Struct Properties' in http://digitalmars.com/d/property.html

(See Note at section bottom).

- Dave

In article <cvg7i9$1cmt$1@digitaldaemon.com>, jicman says...
>
>
>Let us admire this partial code,
>
>class User
>{
>char [] userID = null;
>char [] fname = null;
>char [] lname = null;
>char [] NameOut  = null;
>FCount forms[] = null;
>}
>class FCount
>{
>char[] FormApp = "Language";
>int    FormCnt = 0;
>}
>User ProcessUserForms(char[] fxml, User u)
>{
>int i = 0;
>bit found = false;
>char[][] t;
>t = std.string.split(fxml,"<Application name=\"");
>t = std.string.split(t[1],".Applicat");
>t = std.string.split(t[0],"applications.");
>if(u.forms == null) //.length < 1)
>{
>FCount fc = new FCount();
>u.forms.length = 1;
>u.forms[0] = fc;
>u.forms[0].FormApp = t[1];
>u.forms[0].FormCnt = 1;
>found = true;
>}
>else
>{
>for(i=0; i < u.forms.length; i++)
>{
>if(std.string.cmp(u.forms[i].FormApp,t[1]) == 0)
>{
>found = true;
>u.forms[i].FormCnt++;
>break;
>}
>}
>if(!found)
>{
>FCount fc = new FCount();
>u.forms.length = u.forms.length + 1; // observe this line
>u.forms[length - 1] = fc;
>u.forms[length - 1].FormApp = t[1];
>u.forms[length - 1].FormCnt = 1;
>}
>}
>return u;
>}
>
>This code compiles perfecty, but if I change this line
>
>u.forms.length = u.forms.length + 1; // observe this line
>
>almost at the end, to
>
>u.forms.length += 1; // observe this line
>
>the compiler fails with
>
>16:03:50.47>dmd DTSP1.d ws2_32.lib
>DTSP1.d(740): u.forms.length is not an lvalue
>
>Also, the same happens to,
>
>u.forms.length++;
>
>I just want to understand why.
>
>thanks.
>
>josé
>
>
>
>

Dave says...
>
>The array length is considered a property of an array and so is consistent with properties as described under 'Class and Struct Properties' in http://digitalmars.com/d/property.html
>
>(See Note at section bottom).
>
>- Dave

thanks Dave.

On Tue, 22 Feb 2005 21:18:01 +0000 (UTC), jicman wrote:

> Let us admire this partial code,
> 
> class User
> {
> char [] userID = null;
> char [] fname = null;
> char [] lname = null;
> char [] NameOut  = null;
> FCount forms[] = null;
> }
> class FCount
> {
> char[] FormApp = "Language";
> int    FormCnt = 0;
> }
> User ProcessUserForms(char[] fxml, User u)
> {
> int i = 0;
> bit found = false;
> char[][] t;
> t = std.string.split(fxml,"<Application name=\"");
> t = std.string.split(t[1],".Applicat");
> t = std.string.split(t[0],"applications.");
> if(u.forms == null) //.length < 1)
> {
> FCount fc = new FCount();
> u.forms.length = 1;
> u.forms[0] = fc;
> u.forms[0].FormApp = t[1];
> u.forms[0].FormCnt = 1;
> found = true;
> }
> else
> {
> for(i=0; i < u.forms.length; i++)
> {
> if(std.string.cmp(u.forms[i].FormApp,t[1]) == 0)
> {
> found = true;
> u.forms[i].FormCnt++;
> break;
> }
> }
> if(!found)
> {
> FCount fc = new FCount();
> u.forms.length = u.forms.length + 1; // observe this line
> u.forms[length - 1] = fc;
> u.forms[length - 1].FormApp = t[1];
> u.forms[length - 1].FormCnt = 1;
> }
> }
> return u;
> }
> 
> This code compiles perfecty, but if I change this line
> 
> u.forms.length = u.forms.length + 1; // observe this line
> 
> almost at the end, to
> 
> u.forms.length += 1; // observe this line
> 
> the compiler fails with
> 
> 16:03:50.47>dmd DTSP1.d ws2_32.lib
> DTSP1.d(740): u.forms.length is not an lvalue
> 
> Also, the same happens to,
> 
> u.forms.length++;
> 
> I just want to understand why.
> 
> thanks.
> 
> josé

The 'length' is a property (thus it is really a function call) so it is
like saying ...

   u.forms.length()++;

which is not supported because a function call is not an lvalue.

That's why 'u.forms.length += 1' also fails. But the approved method

  u.forms.length = u.form.length + 1;

is like saying ...

  u.forms.length( u.forms.length() + 1 );

which is okay to use.

-- 
Derek
Melbourne, Australia
23/02/2005 9:31:49 AM