From bug-request at octave dot org Thu Dec  1 14:36:12 2005
Subject: double should not show usage on cell conversion
From: "John W. Eaton" <jwe at bevo dot che dot wisc dot edu>
To: Bill Denney <denney at seas dot upenn dot edu>
Cc: bug at octave dot org
Date: Thu, 1 Dec 2005 15:36:06 -0500

On 16-Nov-2005, Bill Denney wrote:

| When I tried to use double to convert a numeric cell array using curly 
| braces {} to a double array, it failed and showed the usage info for 
| double.  I think that it should work like it does for a regular cell, or 
| preferably it should try to convert if it's a simple conversion of either 
| scalars in every cell or a row or column with equal length columns or rows 
| to a matrix.
| 
| Below is the transcript of what happens.
| 
| I know that octave-forge has cell2mat, but I just wasn't thinking of that 
| one at the moment when I tried this.
| 
| Bill
| 
| octave:1> mycells = {1 2 3 4}
| mycells =
| 
| {
|    [1,1] = 1
|    [1,2] = 2
|    [1,3] = 3
|    [1,4] = 4
| }
| 
| octave:2> class(mycells)
| ans = cell
| octave:3> double(mycells)
| error: invalid conversion from cell to matrix
| octave:3> double(mycells{:})
| 
| *** double:
| 
|   -- Built-in Function:  double (X)
|       Convert X to double precision type.

I don't think this is a bug.  There is no conversion of cell to double
(matrix), so I think the first error is correct.  The second happens
because

  mycells{:}

produces a comma-separated list (i.e., an argument list with
numel(mycells) distinct values) not a "double array".  So

  double (mycells{:})

is equivalent to

  double (1, 2, 3, 4)

which is a usage error because double expects a single argument.

jwe



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