Number of elements is an array

**Tom Serface** · Nov 17 '05, 05:48 PM

Re: Number of elements is an array

Of course, an obvious solution is to do something like:

#define POINT_ARRAY_SZ 3

Point point[] = new Point[POINT_ARRAY_SZ];

Then you could use it anywhere you want.

Tom

"Peter Oliphant" <poliphant@Roun dTripInc.com> wrote in message
news:eQMlId02FH A.632@TK2MSFTNG P10.phx.gbl...[color=blue]
> Say I have a line in my code something like the following (NOTE: Point is
> __value class System::Drawing ::Point):
>
> Point point[] = new Point[3] ;
>
> How do I now 'ask' 'point' how many elements it has (in this case the
> answer is 3)?
>
> This does NOT work:
>
> int element_count = sizeof(point) ; // error C3608: can't apply sizeof to
> a __gc array
>
> Thanks in advance!!! : )
>
> [==P ==]
>[/color]

**James Park** · Nov 17 '05, 05:48 PM

Re: Number of elements is an array

point->Length

"Peter Oliphant" <poliphant@Roun dTripInc.com> wrote in message
news:eQMlId02FH A.632@TK2MSFTNG P10.phx.gbl...[color=blue]
> Say I have a line in my code something like the following (NOTE: Point is
> __value class System::Drawing ::Point):
>
> Point point[] = new Point[3] ;
>
> How do I now 'ask' 'point' how many elements it has (in this case the
> answer is 3)?
>
> This does NOT work:
>
> int element_count = sizeof(point) ; // error C3608: can't apply sizeof to
> a __gc array
>
> Thanks in advance!!! : )
>
> [==P ==]
>[/color]

**Peter Oliphant** · Nov 17 '05, 05:48 PM

Re: Number of elements is an array

> #define POINT_ARRAY_SZ 3[color=blue]
>
> Point point[] = new Point[POINT_ARRAY_SZ];
>
> Then you could use it anywhere you want.[/color]

Hi Tom,

I see what you're saying, but what I need is the ability to find out the
number of elements in an *arbitrary* array. Put another way, when the number
of elements in the array is defined at runtime and is a variable.

This is exactly what I want to be able to do:

int Array_Size( Point point[] )
{
return number_of_eleme nts_in( point ) ;
}

To put this in context, I'm using the Graphics DrawPolygon method. Here it
takes as a parameter Point[], the list of the vertices of the polygon. But
the function does not take the number of elements in Point[] as a parameter,
hence DrawPoygon() must be able to figure out the number of elements in
Point[] just from Point[] (rather, an instance of). I need to be able to do
the same since I must process these points before I give them to
DrawPolygon, so of course I need to know the number of elements in Point[]
as well from the same info (i.e., I'm not given the Point array size in
number of elements).

"Tom Serface" <tserface@msn.c om> wrote in message
news:%23RjCNw02 FHA.2816@tk2msf tngp13.phx.gbl. ..[color=blue]
> Of course, an obvious solution is to do something like:
>
> #define POINT_ARRAY_SZ 3
>
> Point point[] = new Point[POINT_ARRAY_SZ];
>
> Then you could use it anywhere you want.
>
> Tom
>
> "Peter Oliphant" <poliphant@Roun dTripInc.com> wrote in message
> news:eQMlId02FH A.632@TK2MSFTNG P10.phx.gbl...[color=green]
>> Say I have a line in my code something like the following (NOTE: Point is
>> __value class System::Drawing ::Point):
>>
>> Point point[] = new Point[3] ;
>>
>> How do I now 'ask' 'point' how many elements it has (in this case the
>> answer is 3)?
>>
>> This does NOT work:
>>
>> int element_count = sizeof(point) ; // error C3608: can't apply sizeof to
>> a __gc array
>>
>> Thanks in advance!!! : )
>>
>> [==P ==]
>>[/color]
>
>[/color]

**Peter Oliphant** · Nov 17 '05, 05:48 PM

Re: Number of elements is an array

Hi James,

Unfortunately points->Length doesn't work, but instead generates the error:

C2039: 'Length' is not a member of 'System::Drawin g::Point'.

And I've tried 'length', 'size', and 'Size' as well, with no luck.

There HAS to be way to get the number of elements in a Point[] array, but
what is it?

[==P==]

"James Park" <someone@hotmai l.com> wrote in message
news:OicdkI12FH A.3296@TK2MSFTN GP09.phx.gbl...[color=blue]
> point->Length
>
> "Peter Oliphant" <poliphant@Roun dTripInc.com> wrote in message
> news:eQMlId02FH A.632@TK2MSFTNG P10.phx.gbl...[color=green]
>> Say I have a line in my code something like the following (NOTE: Point is
>> __value class System::Drawing ::Point):
>>
>> Point point[] = new Point[3] ;
>>
>> How do I now 'ask' 'point' how many elements it has (in this case the
>> answer is 3)?
>>
>> This does NOT work:
>>
>> int element_count = sizeof(point) ; // error C3608: can't apply sizeof to
>> a __gc array
>>
>> Thanks in advance!!! : )
>>
>> [==P ==]
>>[/color]
>
>[/color]

**Peter Oliphant** · Nov 17 '05, 05:48 PM

Re: Number of elements is an array

My apologies, I was using it wrong. point->Length DOES work. Thanks! : )

[==P=]]

"Tom Serface" <tserface@msn.c om> wrote in message
news:%23RjCNw02 FHA.2816@tk2msf tngp13.phx.gbl. ..[color=blue]
> Of course, an obvious solution is to do something like:
>
> #define POINT_ARRAY_SZ 3
>
> Point point[] = new Point[POINT_ARRAY_SZ];
>
> Then you could use it anywhere you want.
>
> Tom
>
> "Peter Oliphant" <poliphant@Roun dTripInc.com> wrote in message
> news:eQMlId02FH A.632@TK2MSFTNG P10.phx.gbl...[color=green]
>> Say I have a line in my code something like the following (NOTE: Point is
>> __value class System::Drawing ::Point):
>>
>> Point point[] = new Point[3] ;
>>
>> How do I now 'ask' 'point' how many elements it has (in this case the
>> answer is 3)?
>>
>> This does NOT work:
>>
>> int element_count = sizeof(point) ; // error C3608: can't apply sizeof to
>> a __gc array
>>
>> Thanks in advance!!! : )
>>
>> [==P ==]
>>[/color]
>
>[/color]

**Peter Oliphant** · Nov 17 '05, 05:48 PM

Re: Number of elements is an array

My apologies, I was using it wrong. point->Length DOES work. Thanks! : )

[==P=]

"Peter Oliphant" <poliphant@Roun dTripInc.com> wrote in message
news:%238tXbu82 FHA.3188@TK2MSF TNGP12.phx.gbl. ..[color=blue]
> Hi James,
>
> Unfortunately points->Length doesn't work, but instead generates the
> error:
>
> C2039: 'Length' is not a member of 'System::Drawin g::Point'.
>
> And I've tried 'length', 'size', and 'Size' as well, with no luck.
>
> There HAS to be way to get the number of elements in a Point[] array, but
> what is it?
>
> [==P==]
>
> "James Park" <someone@hotmai l.com> wrote in message
> news:OicdkI12FH A.3296@TK2MSFTN GP09.phx.gbl...[color=green]
>> point->Length
>>
>> "Peter Oliphant" <poliphant@Roun dTripInc.com> wrote in message
>> news:eQMlId02FH A.632@TK2MSFTNG P10.phx.gbl...[color=darkred]
>>> Say I have a line in my code something like the following (NOTE: Point
>>> is __value class System::Drawing ::Point):
>>>
>>> Point point[] = new Point[3] ;
>>>
>>> How do I now 'ask' 'point' how many elements it has (in this case the
>>> answer is 3)?
>>>
>>> This does NOT work:
>>>
>>> int element_count = sizeof(point) ; // error C3608: can't apply sizeof
>>> to a __gc array
>>>
>>> Thanks in advance!!! : )
>>>
>>> [==P ==]
>>>[/color]
>>
>>[/color]
>
>[/color]

**Peter Oliphant** · Nov 17 '05, 05:48 PM

Re: Number of elements is an array

Ok, got another question. How do I return a Point[] (pointer) from a method?
The following won't work:

Point[] Get_Points() { return m_Points ; } // error: Point[] is not a valid
syntax here

where m_Points is defined by:

Point m_Points[] ;

I CAN return a pointer to the first element of the list, but I'm guessing
this doesn't retain the array info (such as 'Length'....heh e). That is, I
CAN do the following:

Point* Get_Points() { return &(m_Points[0]) ; }

Is there a way to return a pointer to an array of Point's? Will the above do
the trick and preserve its interpretation of the return value as a pointer
to an array, not just a single element (which I doubt, but it might know
from context)?

Thanks (again) in advance! : )

[==P==]

"James Park" <someone@hotmai l.com> wrote in message
news:OicdkI12FH A.3296@TK2MSFTN GP09.phx.gbl...[color=blue]
> point->Length
>
> "Peter Oliphant" <poliphant@Roun dTripInc.com> wrote in message
> news:eQMlId02FH A.632@TK2MSFTNG P10.phx.gbl...[color=green]
>> Say I have a line in my code something like the following (NOTE: Point is
>> __value class System::Drawing ::Point):
>>
>> Point point[] = new Point[3] ;
>>
>> How do I now 'ask' 'point' how many elements it has (in this case the
>> answer is 3)?
>>
>> This does NOT work:
>>
>> int element_count = sizeof(point) ; // error C3608: can't apply sizeof to
>> a __gc array
>>
>> Thanks in advance!!! : )
>>
>> [==P ==]
>>[/color]
>
>[/color]

**Arnaud Debaene** · Nov 17 '05, 05:48 PM

Re: Number of elements is an array

Peter Oliphant wrote:[color=blue]
> Ok, got another question. How do I return a Point[] (pointer) from a
> method? The following won't work:
>
> Point[] Get_Points() { return m_Points ; } // error: Point[] is not a
> valid syntax here[/color]

Point Get_Points() []
{ return m_Points ; }

Geee, *why* oh why did they choose to keep this awfull K&R syntax ;-(

Arnaud
MVP - VC

**Peter Oliphant** · Nov 17 '05, 05:48 PM

Re: Number of elements is an array

> Point Get_Points() [][color=blue]
> { return m_Points ; }[/color]

I never in a million years would have tried that syntax...but it definitely
works...Thanks! !! : )

[==P==]

"Arnaud Debaene" <adebaene@clu b-internet.fr> wrote in message
news:uxTPpY%232 FHA.2640@TK2MSF TNGP09.phx.gbl. ..[color=blue]
> Peter Oliphant wrote:[color=green]
>> Ok, got another question. How do I return a Point[] (pointer) from a
>> method? The following won't work:
>>
>> Point[] Get_Points() { return m_Points ; } // error: Point[] is not a
>> valid syntax here[/color]
>
> Point Get_Points() []
> { return m_Points ; }
>
> Geee, *why* oh why did they choose to keep this awfull K&R syntax ;-(
>
> Arnaud
> MVP - VC
>
>[/color]

**Tom Serface** · Nov 17 '05, 05:48 PM

Re: Number of elements is an array

Sorry Peter, didn't understand your requirement. Length would be the way to
go in this case. I thought you were using a generic example.

Tom

"Peter Oliphant" <poliphant@Roun dTripInc.com> wrote in message
news:ezPCls82FH A.1148@tk2msftn gp13.phx.gbl...[color=blue][color=green]
>> #define POINT_ARRAY_SZ 3
>>
>> Point point[] = new Point[POINT_ARRAY_SZ];
>>
>> Then you could use it anywhere you want.[/color]
>
> Hi Tom,[/color]

**Arnaud Debaene** · Nov 17 '05, 05:48 PM

Re: Number of elements is an array

Peter Oliphant wrote:[color=blue][color=green]
>> Point Get_Points() []
>> { return m_Points ; }[/color]
>
> I never in a million years would have tried that syntax...[/color]

Well, RTFM ;-)

http://msdn.microsoft.com/library/default.asp?url=/library/en-us/vcmxspec/html/vcManagedExtensionsSpec_4_5_2.asp

Arnaud
MVP - VC

Number of elements is an array

Number of elements is an array

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