Assigning a Reference to a Variable

[Drakemar]

Hello all,
Thank you for taking the time to read and help me with my question.

Here is a simplified program I have:


int[,] array2D = { {1, 2, 3}, {4, 5, 6} };


private void Main(){
printarray2DVal ue(0);
printarray2DVal ue(1);
}

printarray2DVal ue(int dValue){
int length;
int i=0;
int x;
int y;
string str;

if (dValue==0){
length = array2D .GetLength(0);
x=i;
y=0;
}
else{
length = array2D .GetLength(1);
x=0;
y=1;
}

for (i;i<length;i++ ){
str += 2dArray[x,y].ToString();
}
MessageBox.Show (str);
}

Now, that obviously doesn't work how I would want it to. And I can't
say "x= ref i" either because C# won't allow it. I read
http://www.yoda.arachsys.com/csharp/parameters.html, and

http://groups.google.ca/group/microsoft.public.dotnet.languages.csharp/browse_thread/thread/d6a1f2a1e4d25f79/18c83a169e66dacb?hl=en&lnk=gst&q=reference+variable#18c83a169e66dacb

and I believe my answer is that I can not do what I want, unless I use
unsafe code, or boxing.

The easiest solution is just to split this into two methods, one for
each dimension of the array. But, the more dimensions, the more
methods, and thats not good.

Any suggestions?

[Jon Skeet [C# MVP]]

Re: Assigning a Reference to a Variable

On May 14, 2:10 pm, Drakemar <mdeve...@hotma il.comwrote:

Thank you for taking the time to read and help me with my question.
>
Here is a simplified program I have:

<snip>

Given that this *doesn't* do what you want it to, could you explain
what you *do* want to achieve? It's not really clear to me at the
moment.

Jon

[Ignacio Machin ( .NET/ C# MVP )]

Re: Assigning a Reference to a Variable

Now, that obviously doesn't work how I would want it to.  And I can't
say "x= ref i" either because C# won't allow it.  I readhttp://www.yoda.arachs ys.com/csharp/parameters.html , andhttp://groups.google.c a/group/microsoft.publi c.dotnet.langua ges.cshar...
and I believe my answer is that I can not do what I want, unless I use
unsafe code, or boxing.

What wyo uwant to do in the first place? It seems like if you want to
print all the members of one of the given dimensions, but if this is
the case it's pretty convoluted way that you selected.

The easiest solution is just to split this into two methods, one for
each dimension of the array.  But, the more dimensions, the more
methods, and thats not good.

Your code neither works with more than two dimensions to start with.

Any suggestions?

What are you tryong to do?

[Peter Duniho]

Re: Assigning a Reference to a Variable

On Wed, 14 May 2008 06:10:25 -0700, Drakemar <mdeverno@hotma il.comwrote:

[...]
for (i;i<length;i++ ){
str += 2dArray[x,y].ToString();

I have the impression that in this loop, you want "x" to either remain
constant (0, if "dValue" is non-zero) or to follow the value of "i" (if
"dValue" is zero).

This particular example seems odd to me (for one, if "dValue" is non-zero,
then you just keep using the same array element over and over). But
assuming I've understood correctly, there is no direct way to accomplish
what you want.

IMHO, the most straight-forward approach would be to simply break the task
out into two different methods, one for each scenario. Assuming your code
example is truly representative, you'd wind up with very little extra
lines of code (since you'd get rid of some of the initialization code),
and it would probably be more obvious what the intent of the code is.

One alternative is to define an expression that can be evaluated as
needed. For example:

Func<intx;

if (dValue == 0)
{
length = array2D .GetLength(0);
x = x1 =i;
y = 0;
}
else
{
length = array2D .GetLength(1);
x = x1 =0;
y = 1;
}

for (i; i < length; i++)
{
str += 2dArray[x, y].ToString();
}

Then instead of being a simple variable, "x" is essentially a delegate
that can be executed as necessary. If "dValue" is 0, it will return the
current value of "i". If not, it will always return 0.

As the other replies suggest, your question is not easy to understand. If
the above isn't helpful, you should try to post some code that really does
exactly what you want, even if in a less elegant way than you'd desire, or
at least be MUCH more specific about what you feel the correct output
would be. Posting code that doesn't work isn't the best way to convey
what it is you _do_ want to happen. :)

Pete

[Drakemar]

Re: Assigning a Reference to a Variable

I apologize for my utterly unclear example=).

Basically, what I wanted was to have a single function iterate through
the two-dimensional array in a certain dimension based on one
parameter.
So, with the following code, I was wanting to have
printarray2DVal ue(0) output "123", and printarray2DVal ue(0) output
"14".

int[,] array2D = { {1, 2, 3}, {4, 5, 6} };

private void Main(){
printarray2DVal ue(0);
printarray2DVal ue(1);

}

printarray2DVal ue(int dValue){
int length;
int i=0;
int x;
int y;
string str;

if (dValue==0){
length = array2D .GetLength(0);
x=i;
y=0;
}
else{
length = array2D .GetLength(1);
x=0;
y=i; //note, this was a typo my first post. I wrote 1 when I
should have wrote i.
}

for (i;i<length;i++ ){
str += 2dArray[x,y].ToString();
}

MessageBox.Show (str);

}


I looked more into the Func<intthat you suggested and found that the
following solved the problem for me:
int[,] array2D = { {1, 2, 3}, {4, 5, 6} };

private void Main(){
printarray2DVal ue(0);
printarray2DVal ue(1);

}

printarray2DVal ue(int dValue){
int length;
int i=0;
int x;
int y;
string str;
Func<intxLoc;
Func<intyLoc;

if (dValue==0){
length = array2D .GetLength(0);
xLoc = (()=>i);
yLoc=0;
}
else{
length = array2D .GetLength(1);
xLoc =0;
yLoc= (()=>i);
}
x = xLoc;
y=yLoc;

for (i;i<length;i++ ){
str += 2dArray[x(),y()].ToString();
}

MessageBox.Show (str);

}

[Jon Skeet [C# MVP]]

Re: Assigning a Reference to a Variable

On May 16, 1:55 pm, Drakemar <mdeve...@hotma il.comwrote:

I apologize for my utterly unclear example=).
>
Basically, what I wanted was to have a single function iterate through
the two-dimensional array in a certain dimension based on one
parameter.
So, with the following code, I was wanting to have
printarray2DVal ue(0) output "123", and printarray2DVal ue(0) output
"14".

Hang on - so you're talking about going in a different *direction*
rather than just effectively slicing different rows out of a
rectangle?

Jon

[Peter Duniho]

Re: Assigning a Reference to a Variable

On Fri, 16 May 2008 05:55:07 -0700, Drakemar <mdeverno@hotma il.comwrote:

[...]
I looked more into the Func<intthat you suggested and found that the
following solved the problem for me:

Glad it worked. Sorry for the bad syntax in my post...I was rushing, with
predictable consequences. :)

I'll second Jon's sentiment that the actual implementation here seems
weird. But assuming that's really what you want to do, it seems that this
should work fine.

Pete

[Alun Harford]

Re: Assigning a Reference to a Variable

Peter Duniho wrote:

On Wed, 14 May 2008 06:10:25 -0700, Drakemar <mdeverno@hotma il.comwrote:
>

>[...]
> for (i;i<length;i++ ){
> str += 2dArray[x,y].ToString();

>
I have the impression that in this loop, you want "x" to either remain
constant (0, if "dValue" is non-zero) or to follow the value of "i" (if
"dValue" is zero).
>
This particular example seems odd to me (for one, if "dValue" is
non-zero, then you just keep using the same array element over and
over). But assuming I've understood correctly, there is no direct way
to accomplish what you want.

I accept your challenge! :-)

static void printarray2DVal ue(int dValue)
{
int length;
int i = 0, zero = 0;
TypedReference x, y;
string str="";

if (dValue == 0)
{
length = array2D.GetLeng th(0);
x = __makeref(i);
y = __makeref(zero) ;
}
else
{
length = array2D.GetLeng th(1);
x = __makeref(zero) ;
y = __makeref(i);
}

for (; i < length; i++)
{
str += array2D[__refvalue(x, int), __refvalue(y, int)].ToString();
}

MessageBox.Show (str);
}

Alun Harford