Looking for a C++ class.

[JustSomeGuy]

I need a class that is essentially a matrix (template) class.
I need to be able add rows and columns as needed.
any one know of such a class?

[Victor Bazarov]

Re: Looking for a C++ class.

JustSomeGuy wrote:[color=blue]
> I need a class that is essentially a matrix (template) class.
> I need to be able add rows and columns as needed.
> any one know of such a class?[/color]

Yes, I know of a matrix class (or two, or three). What do you mean
"add rows and columns as needed"?

V

[JustSomeGuy]

Re: Looking for a C++ class.

Victor Bazarov wrote:
[color=blue]
> JustSomeGuy wrote:[color=green]
> > I need a class that is essentially a matrix (template) class.
> > I need to be able add rows and columns as needed.
> > any one know of such a class?[/color]
> adding
> Yes, I know of a matrix class (or two, or three). What do you mean
> "add rows and columns as needed"?[/color]

Imaging a table with each row being a directory and each column being a
user name.
As I traverse the file system and find new directories i will be adding
rows to the Matrix.
As i traverse each file within the directory I will be getting the user
name of the person who
owns the file. As new owners are found a column is added to the
Matrix. Each entry in
the Matrix is a sum of the disk space used by that user.

Make sense?

[Victor Bazarov]

Re: Looking for a C++ class.

JustSomeGuy wrote:[color=blue]
> Victor Bazarov wrote:
>
>[color=green]
>>JustSomeGuy wrote:
>>[color=darkred]
>>>I need a class that is essentially a matrix (template) class.
>>>I need to be able add rows and columns as needed.
>>>any one know of such a class?[/color]
>>
>>adding
>>Yes, I know of a matrix class (or two, or three). What do you mean
>>"add rows and columns as needed"?[/color]
>
>
> Imaging a table with each row being a directory and each column being a
> user name.
> As I traverse the file system and find new directories i will be adding
> rows to the Matrix.
> As i traverse each file within the directory I will be getting the user
> name of the person who
> owns the file. As new owners are found a column is added to the
> Matrix. Each entry in
> the Matrix is a sum of the disk space used by that user.
>
> Make sense?[/color]

So, you essentially need an expandable table. It seems that you need some
kind of associative container that has users as keys and directories as
keys as well. The value is the "used space size". I don't think there is
one ready to use. You should roll your own. Shouldn't be that difficult.

class mytable {
std::map<std::s tring, int> indices_of_size s_by_user;
std::map<std::s tring, int> indices_of_size s_by_directory;
std::vector<lon g> sizes;
public:
void adduser(std::st ring const&);
void adddirectory(st d::string const&);
long sumbyuser(std:: string const&) const;
long sumbydirectory( std::string const&) const;
long size(std::strin g const& user, std::string const& dir) const;
};

Just start writing...

V

[Victor Bazarov]

Re: Looking for a C++ class.

JustSomeGuy wrote:[color=blue]
> Victor Bazarov wrote:
>
>[color=green]
>>JustSomeGuy wrote:
>>[color=darkred]
>>>I need a class that is essentially a matrix (template) class.
>>>I need to be able add rows and columns as needed.
>>>any one know of such a class?[/color]
>>
>>adding
>>Yes, I know of a matrix class (or two, or three). What do you mean
>>"add rows and columns as needed"?[/color]
>
>
> Imaging a table with each row being a directory and each column being a
> user name.
> As I traverse the file system and find new directories i will be adding
> rows to the Matrix.
> As i traverse each file within the directory I will be getting the user
> name of the person who
> owns the file. As new owners are found a column is added to the
> Matrix. Each entry in
> the Matrix is a sum of the disk space used by that user.
>
> Make sense?[/color]

So, you essentially need an expandable table. It seems that you need some
kind of associative container that has users as keys and directories as
keys as well. The value is the "used space size". I don't think there is
one ready to use. You should roll your own. Shouldn't be that difficult.

class mytable {
std::map<std::s tring, std::map<std::s tring,int> >
indices_of_size s_by_user;
std::map<std::s tring, std::map<std::s tring,int> >
indices_of_size s_by_directory;
std::vector<lon g> sizes;
public:
void adduser(std::st ring const&);
void adddirectory(st d::string const&);
long sumbyuser(std:: string const&) const;
long sumbydirectory( std::string const&) const;
long size(std::strin g const& user, std::string const& dir) const;
void addsize(std::st ring const& user, std::string const& dir, long);
};

The 'indices_of_siz es_by_user' contains the user name as the primary key
and the directory name as the secondary key. The value is the index of
the size of the space used by that user in that directory.

The 'indices_of_siz es_by_directory ' is a symmetrical table of indices, but
now the primary key is the directory. You don't really need it, only for
sorting purposes since it is going to essentially duplicate the data in
the first one.

The 'sizes' vector is the actual storage of sizes, indexed by the values
from the map[s].

To make sure your 'mytable' class works correctly, remember to add to the
respective maps and to the vector every time you introduce another user or
another directory. The proposed scheme allows you not to keep zero sizes.

Just start implementing it, you'll have fun, trust me...

V

[Thomas Matthews]

Re: Looking for a C++ class.

JustSomeGuy wrote:[color=blue]
> Victor Bazarov wrote:
>
>[color=green]
>>JustSomeGuy wrote:
>>[color=darkred]
>>>I need a class that is essentially a matrix (template) class.
>>>I need to be able add rows and columns as needed.
>>>any one know of such a class?[/color]
>>
>>adding
>>Yes, I know of a matrix class (or two, or three). What do you mean
>>"add rows and columns as needed"?[/color]
>
>
> Imaging a table with each row being a directory and each column being a
> user name.
> As I traverse the file system and find new directories i will be adding
> rows to the Matrix.
> As i traverse each file within the directory I will be getting the user
> name of the person who
> owns the file. As new owners are found a column is added to the
> Matrix. Each entry in
> the Matrix is a sum of the disk space used by that user.
>
> Make sense?
>
>
>[/color]

Search the web for matrix or grid classes.


--
Thomas Matthews

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http://www.sgi.com/tech/stl -- Standard Template Library

[Alf P. Steinbach]

Re: Looking for a C++ class.

* JustSomeGuy:[color=blue]
>
> Imaging a table with each row being a directory and each column being a
> user name.
> As I traverse the file system and find new directories i will be adding
> rows to the Matrix.
> As i traverse each file within the directory I will be getting the user
> name of the person who
> owns the file. As new owners are found a column is added to the
> Matrix. Each entry in
> the Matrix is a sum of the disk space used by that user.
>
> Make sense?[/color]

Yes, but it's not a C++ question (it's off-topic in clc++).

Therefore I've cross-posted to [comp.programmin g] and set follow-up to
there.

The structure in your data is very classic and very simple,

username 1 <---> n sizeitem n <---> 1 directory

What you need at an abstract relational data base level:

Table Usernames row:
[usename (key), sizeitemID (ref)]

Table Directories row:
[directory (key), sizeitemID (ref)]

Table SizeItems row:
[sizeitemID (key), sizeitem, username (ref), directory (ref)]

Now go implement in C++... ;-)


XFUT: [comp.programmin g]

--
A: Because it messes up the order in which people normally read text.
Q: Why is it such a bad thing?
A: Top-posting.
Q: What is the most annoying thing on usenet and in e-mail?

[Alf P. Steinbach]

Re: Looking for a C++ class.

* Alf P. Steinbach:[color=blue]
> * JustSomeGuy:[color=green]
> >
> > Imaging a table with each row being a directory and each column being a
> > user name.
> > As I traverse the file system and find new directories i will be adding
> > rows to the Matrix.
> > As i traverse each file within the directory I will be getting the user
> > name of the person who
> > owns the file. As new owners are found a column is added to the
> > Matrix. Each entry in
> > the Matrix is a sum of the disk space used by that user.
> >
> > Make sense?[/color]
>
> Yes, but it's not a C++ question (it's off-topic in clc++).
>
> Therefore I've cross-posted to [comp.programmin g] and set follow-up to
> there.
>
> The structure in your data is very classic and very simple,
>
> username 1 <---> n sizeitem n <---> 1 directory
>
> What you need at an abstract relational data base level:
>
> Table Usernames row:
> [usename (key), sizeitemID (ref)]
>
> Table Directories row:
> [directory (key), sizeitemID (ref)]
>
> Table SizeItems row:
> [sizeitemID (key), sizeitem, username (ref), directory (ref)][/color]

Bah, posting in haste. Remove the sizeitemID from the first two
tables.

[color=blue]
> Now go implement in C++... ;-)
>
> XFUT: [comp.programmin g][/color]

--
A: Because it messes up the order in which people normally read text.
Q: Why is it such a bad thing?
A: Top-posting.
Q: What is the most annoying thing on usenet and in e-mail?

[Jonathan Turkanis]

Re: Looking for a C++ class.

JustSomeGuy wrote:
[color=blue]
> Imaging a table with each row being a directory and each column being
> a user name.
> As I traverse the file system and find new directories i will be
> adding rows to the Matrix.
> As i traverse each file within the directory I will be getting the
> user name of the person who
> owns the file. As new owners are found a column is added to the
> Matrix. Each entry in
> the Matrix is a sum of the disk space used by that user.
>
> Make sense?[/color]

Sound like the Boost.MultiInde x library might be appropriate (I can't say for
sure, since I haven't studied it):

http://www.boost.org/libs/multi_index/doc/index.html

Jonathan

[Dave O'Hearn]

Re: Looking for a C++ class.

Jonathan Turkanis wrote:[color=blue]
> Sound like the Boost.MultiInde x library might be appropriate (I
> can't say for sure, since I haven't studied it):
>
> http://www.boost.org/libs/multi_index/doc/index.html[/color]

I agree. I just spent a day evaluating Boost.MultiInde x, and it seems
suitable to replace an entire "relations" library I wrote a year ago,
to build many-to-many and many-to-one relations by composing sets of
sets.

I won't know for sure until I attempt replacing my library with
Boost.MultiInde x, but in general it looks great, and I recommend
keeping it in mind as an alternative anytime composing containers of
containers comes up.

--
Dave O'Hearn