List of data?

[Robert Crandal]

I'm using Excel 2007 and I'm looking for an easy way to
implement something like a linked list of data or as a
set that is found in other programming languages. I would
like to be able to easily add or remove items from this
list data structure. It would also be nice if I could dump
the list data/contents into Excel cells.

Anyone have any ideas or suggestions?

Thank you!

 

[GS]

After serious thinking Robert Crandal wrote :

I'm using Excel 2007 and I'm looking for an easy way to
implement something like a linked list of data or as a
set that is found in other programming languages. I would
like to be able to easily add or remove items from this
list data structure. It would also be nice if I could dump
the list data/contents into Excel cells.

Anyone have any ideas or suggestions?

Thank you!

Robert, can you provide more detail about what you're trying to do AND
what exactly is your definition of 'a linked list'?

 

[Robert Crandal]

Sure, I probably wasnt very clear, so I'll try to just give
the basic gist of what I need.

I was basically wondering if Visual Basic for Excel 2007 has
some sort of data type that can hold a "set" of unique strings.
I would like to be able to add or remove strings from this set
and possibly iterate through the set of strings to see what the
set contains.

I realize that I could use an array of strings to implement a set of
of strings, but that seems to be overkill and possibly time consuming.
So, I'm basically wondering if Visual Basic provides some sort
of a "set" data type or datastructure?? Does that make sense?

Robert

 

[duadinam]

Sure, I probably wasnt very clear, so I'll try to just give
the basic gist of what I need.

I was basically wondering if Visual Basic for Excel 2007 has
some sort of data type that can hold a "set" of unique strings.
I would like to be able to add or remove strings from this set
and possibly iterate through the set of strings to see what the
set contains.

I realize that I could use an array of strings to  implement a set of
of strings, but that seems to be overkill and possibly time consuming.
So, I'm basically wondering if Visual Basic provides some sort
of a "set" data type or datastructure??  Does that make sense?

Robert

I'm looking for something similar. Basically, I want a two
dimensional array with a variable length. I can't believe that VBA
does not have linked list.

david

 

[GS]

Robert Crandal has brought this to us :

Sure, I probably wasnt very clear, so I'll try to just give
the basic gist of what I need.

I was basically wondering if Visual Basic for Excel 2007 has
some sort of data type that can hold a "set" of unique strings.
I would like to be able to add or remove strings from this set
and possibly iterate through the set of strings to see what the
set contains.

I realize that I could use an array of strings to implement a set of
of strings, but that seems to be overkill and possibly time consuming.
So, I'm basically wondering if Visual Basic provides some sort
of a "set" data type or datastructure?? Does that make sense?

Robert

Hi Robert,

That's a bit more helpful but doesn't answer my Q about a 'linked
list'. There is no data type that holds a 'set' of values as you
describe. There are structures you could use to store and manipulate
sets of data; namely an Array() or a Collection would be first chioces
for unknown values/size at runtime. Both of these would let you
add/remove/change the data however required. In both cases, you might
want to store the data in a file (possibly encrypted) so it can be
retrieved at startup and saved at shutdown.

The UDT structure might work for known members at design time but you
can only change the values at runtime (ergo you can't add/remove
members at runtime).

The easiest approach <IMO> would be to use a variable defined as
Variant data type. This would allow you to manipulate the data using
VB[A]'s Split() and Join() functions as well as the Filter() function
to remove blank elements resulting from deleted data. I'd use a
delimited string for each record of data so it fits nicely into a one
dim array. Parsing each record is fairly easy and straight forward
using the Split() function.

Optionally, depending on how the storage is structured, you could use
ADO to manage the data in 'sets' based on criteria you define.

HTH

 

[Robert Crandal]

I know I didnt answer the question about a "linked list". I
thought it would be better if I just forget about linked lists
because it is an abstract data type that is often implemented
in the C/C++ programming language.

Basically, a "linked list" is a set of data structures or "nodes"
that is in sequence; ie, the list has a beginning (i.e "head") and
and an end (i.e "tail"). Each node contains data, in addition
to a "next" pointer which points to the next node in the list.

Below is a text/graphical depiction of a linked list with
6 nodes. H is the head node, T is the tail node, and all
the other nodes are marked as N. Each node has an
arrow or pointer which points to the next node.

[H]-->[N]-->[N]-->[N]-->[N]-->[T]

The nice thing about linked lists is that you can make them
dynamically grow or shink, by adding or deleting nodes.
So, a linked list is ALMOST like an array. The main difference
is that an array size is usually fixed, but a linked list can
dynamically grow and new nodes can be inserted anywhere
in the middle of the list.

Is this really your first experience with linked lists??

 

[GS]

Robert Crandal explained :

I know I didnt answer the question about a "linked list". I
thought it would be better if I just forget about linked lists
because it is an abstract data type that is often implemented
in the C/C++ programming language.

Basically, a "linked list" is a set of data structures or "nodes"
that is in sequence; ie, the list has a beginning (i.e "head") and
and an end (i.e "tail"). Each node contains data, in addition
to a "next" pointer which points to the next node in the list.

Below is a text/graphical depiction of a linked list with
6 nodes. H is the head node, T is the tail node, and all
the other nodes are marked as N. Each node has an
arrow or pointer which points to the next node.

[H]-->[N]-->[N]-->[N]-->[N]-->[T]

The nice thing about linked lists is that you can make them
dynamically grow or shink, by adding or deleting nodes.
So, a linked list is ALMOST like an array. The main difference
is that an array size is usually fixed, but a linked list can
dynamically grow and new nodes can be inserted anywhere
in the middle of the list.

Is this really your first experience with linked lists??

Well, I don't have any experience with linked lists. I'm afraid my
programming experience is limited to VB/VBA, HTML, and some vbScript.
I've read about this while exploring Delphi as a possible candidate for
my next gen dev language. I think it's a great concept, though.

I get a similar effect using a one dim array with [delimited] string
elements. Since arrays don't dynamically resize when deleting the
contents of an element, the Filter() function trims out any empty
elements and returns a newly sized array. For example, if myArray has
10 elements (0 T0 9) and I empty elements 2 and 6, the Filter()
function resizes the array to 8 elements (0 To 7). (What happens is
elements 3-5 shift one position, elements 7-10 shift 2 positions)

This makes for a very flexible structure where, for example, each
element of my one dim array can hold an array (thus making it an array
of arrays) if I choose. Usually, I store delimited strings that I parse
into a temp array when I want to use the data. I find this approach a
bit faster and easier to manage size-wise.

So, for example, if you stored your data in a text file where each
'record' of data was on a separate line then you could quickly dump the
file contents into a 'dynamic' array using Split() and specifying
vbCrLf as the delimiter. (Conversely, writing back is a simple matter
of using Join() and specifying vbCrLf as the delimiter) I like to store
field names (headings) in the first row so element 1 of myArray is the
first record and UBound(myArray) is the number of records. It also
makes it easier to dump the data onto a spreadsheet. (..subject to
worksheet row limit)

 

[Pete_UK]

Hi Robert,

when I taught data structures in the 1980's I used BBC Basic to
demonstrate how a linked list structure could be implemented. A 1-D
string array was used to hold the data and a numeric array held the
pointers. In addition, a free-space pointer pointed to the next
available element of the array. As data was added (in any order) the
pointers were adjusted to maintain the correct sequence. If data is
deleted then the free space pointer is adjusted, along with the
pointer of the element which is removed and the pointer which pointed
to that element. It can also be beneficial to have another set of
pointers which point back to the previous data item, so that the list
can be searched in both directions.

I haven't tried to implement this using VBA, but similar approaches
could be taken.

Hope this helps.

Pete

I know I didnt answer the question about a "linked list".  I
thought it would be better if I just forget about linked lists
because it is an abstract data type that is often implemented
in the C/C++ programming language.

Basically, a "linked list" is a set of data structures or "nodes"
that is in sequence; ie, the list has a beginning (i.e "head") and
and an end (i.e "tail").  Each node contains data, in addition
to a "next" pointer which points to the next node in the list.

Below is a text/graphical depiction of a linked list with
6 nodes.  H is the head node, T is the tail node, and all
the other nodes are marked as N.  Each node has an
arrow or pointer which points to the next node.

  [H]-->[N]-->[N]-->[N]-->[N]-->[T]

The nice thing about linked lists is that you can make them
dynamically grow or shink, by adding or deleting nodes.
So, a linked list is ALMOST like an array.  The main difference
is that an array size is usually fixed, but a linked list can
dynamically grow and new nodes can be inserted anywhere
in the middle of the list.

Is this really your first experience with linked lists??

That's a bit more helpful but doesn't answer my Q about a 'linked list'..- Hide quoted text -

- Show quoted text -