From bug-octave-request at bevo dot che dot wisc dot edu  Thu Nov  5 07:49:19 1998
Subject: Problems with arrays of strings
From: "John W. Eaton" <jwe at bevo dot che dot wisc dot edu>
To: Francesco Potorti` <F dot Potorti at cnuce dot cnr dot it>
Cc: Octave bugs list <bug-octave at bevo dot che dot wisc dot edu>
Date: Thu, 5 Nov 1998 07:47:53 -0600 (CST)

On  5-Nov-1998, Francesco Potorti` <F dot Potorti at cnuce dot cnr dot it> wrote:

| I read in the octave manual:
| 
|  - Function File:  str2mat (S_1, ..., S_N)
|      Return a matrix containing the strings S_1, ..., S_N as its rows.
|      Each string is padded with blanks in order to form a valid matrix.
| 
|      *Note:* This function is modelled after MATLAB.  In Octave, you
|      can create a matrix of strings by `[S_1; ...; S_N]' even if the
|      strings are not all the same length.
| 
| but:
| 
| octave:2> x=["a";"ab"]
| x =
| 
| a 
| ab
| 
| octave:4> y=x(1,:)
| y = a 
| octave:5> length(y)
| ans = 2        <-- strings are all the same length, contrary to what I expected
| octave:7> strcat("`",y,"'")
| ans = `a '
| octave:8> version
| ans = 2.0.13.91

Perhaps the docs should be clearer.  Both

  str2mat ("a", "ab")

and

  ["a"; "ab"]

are equivalent in Octave.  They both pad with blanks.  You can use the
deblank function to strip them off.  I know it's inconvenient, but I
don't know how to fix this for arrays of strings/character matrices
and still be compatible with Matlab.

| Moreover, running this script I get:
| 
| ---------- test.sh -------
| #! /usr/bin/octave -qf
| [argv(1,:), ".inp"]
| --------------------------
| $ test.sh td6 25407 1025724
| ans = td6

The problem here is that because of an oversight on my part, Octave
pads the argv vector with 0 instead of blanks.  I'm not sure whether
that is worth fixing for the 2.0.x series.  In Octave 2.1.x (x > 8)
argv is implemented as a list of strings, so this problem is avoided.

| and I also get an internal error from octave running the script appended:
| 
| $ make_markov_inp.sh td6 25407 1025724
| ofile = td6
| error: octave_char_matrix_str::valid_as_scalar_index(): not implemented
| error: string type invalid as index value
| error: evaluating index expression near line 108, column 16
| error: evaluating assignment expression near line 108, column 14
| error: called from `make_markov_inp' in file `/home/foda/fracas/make_markov_inp.m'

I think the problem is that you have used the name `stat' as a
variable and then you are trying to call it as a function.  Once
you've used the name as a variable, Octave thinks you are trying to
index the variable instead of call the function

|     stat = find (abs(diag(l)-1) < sqrt(eps)); # Locate eigenvalues equal to 1

| ...

|     ofile = [ifile, ".inp"]
|     [s, err] = stat (ofile)


jwe