Re: Creating a varargin-like object

[Miquel Cabanas]

hi,

On Mon, 2006-02-20 at 00:50 -0500, Edward C. Jones wrote:
> I use the Debian package octive2.1 version 1:2.1.72-10.

Debian is great! it's actually so great that it comes with all the
answers to your questions. For that you should have installed the
packages,

octave2.1-htmldoc  - HTML documentation on the GNU Octave lang
octave2.1-info     - GNU Info documentation on the GNU Octave

You can access the HTML documentation from http://localhost/dwww ,
search for "octave" in the "Debian documentation Menu". Afterwards,
select the "The GNU Octave Manual". You could try and see if the link
below works for you,

http://localhost/cgi-bin/dwww?type=html&location=/usr/share/doc/octave2.1-htmldoc/octave_toc.html

If you want too a printed copy of the manual, install

octave2.1-doc      - PDF documentation on the GNU Octave langu


> What kind of an object is c{:}? Note the curly brackets.

It's a container called "cell array". For more information, see Chapter
7 in the manual,

http://localhost/cgi-bin/dwww?type=file&location=/usr/share/doc/octave2.1-htmldoc/octave_8.html

> The octave source code is full of stuff like:
> 
> function plot (varargin)
>    __plt__ ("plot", varargin{:});
> 
> Why are the curly brackets used?
> 

varargin is a built-in cell array used to pass an arbitrary number of
arguments to a function. In this case, you will find a more in depth
explanation in the Octave wiki,

http://wiki.octave.org/wiki.pl?VariableLengthArgumentLists

> Suppose I have a collection of strings 'A', 'B', ... What should XXX be in
> the following:
>      XXX = ?????
>      menu('sometext', XXX)
> so that the choices in the menu are 'A', 'B', etc. In other words, how do I
> create a varargin-like object from scratch?

I'm not sure to understand your question, the menu() function is used to
display a menu on screen and to prompt for a valid answer. For instance
(a clearly unbiased question)

octave:1> reply = menu("Do you like Octave?", "yes", "absolutely", "it's
great");

Do you like Octave?

  [ 1] yes
  [ 2] absolutely
  [ 3] it's great

pick a number, any number: 3
octave:2> reply
reply = 3

As for creating a cell array, you should use the functions cell()
---that you used in your message--- and cellstr(). Maybe this later is
what you're looking for. First you create a string array,

octave:3> strarray = [ "a" "b" "c" "d"]'
strarray =

a
b
c
d

Note the transpose, otherwise the array elements will be concatenated
into a single string. Then you use the cellstr() function to build a
cell array,

octave:4> cellstr (strarray)
ans =

{
  [1,1] = a
  [2,1] = b
  [3,1] = c
  [4,1] = d
}


Hope this helps,

Miquel






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