Division by zero in rat/rats

[Atanas Atanasov-5]

Bug report for Octave 3.0.0 configured for x86_64-pc-linux-gnu

Description:
-----------

The functions rat and rats should handle the special case of zero  
input, which it seems currently they do not do. As a result the user  
recieves a 'warning: division by zero' and wrong output.

Repeat-By:
---------

rat(0)
[p,q] = rat(0)
rats(0)

Fix:
---

It is possible to check whether the input is zero before calling  
rat/rats but this is tedious. The check should be incorporated in the  
beginning of rat.m.

Configuration (please do not edit this section):
-----------------------------------------------

uname output:     Linux serre 2.6.24-18-generic #1 SMP Wed May 28  
19:28:38 UTC 2008 x86_64 GNU/Linux
configure opts:   '--host=x86_64-linux-gnu' '--build=x86_64-linux-gnu'  
'--prefix=/usr' '--datadir=/usr/share' '--libdir=/usr/lib'  
'--libexecdir=/usr/lib' '--infodir=/usr/share/info'  
'--mandir=/usr/share/man' '--with-blas=-lblas-3gf'  
'--with-lapack=-llapackgf-3' '--with-hdf5' '--with-fftw'  
'--enable-shared' '--enable-rpath' '--disable-static'  
'build_alias=x86_64-linux-gnu' 'host_alias=x86_64-linux-gnu' 'CC=gcc'  
'CFLAGS=-g -O2' 'LDFLAGS=-Wl,-Bsymbolic-functions' 'CPPFLAGS='  
'CXX=g++' 'CXXFLAGS=-g -O2' 'F77=gfortran' 'FFLAGS=-g -O2'
Fortran compiler: gfortran
FFLAGS:           -O2
F2C:              @F2C@
F2CFLAGS:         @F2CFLAGS@
FLIBS:            -L/usr/lib/gcc/x86_64-linux-gnu/4.2.3  
-L/usr/lib/gcc/x86_64-linux-gnu/4.2.3/../../../../lib64  
-L/lib/../lib64 -L/usr/lib/../lib64  
-L/usr/lib/gcc/x86_64-linux-gnu/4.2.3/../../.. -lhdf5 -lz  
-lgfortranbegin -lgfortran -lm
CPPFLAGS:
INCFLAGS:         -I. -I. -I./liboctave -I./src -I./libcruft/misc
C compiler:       gcc, version 4.2.3 (Ubuntu 4.2.3-2ubuntu6)
CFLAGS:           -O2
CPICFLAG:         -fPIC
C++ compiler:     g++, version 4.2.3
CXXFLAGS:         -O2
CXXPICFLAG:       -fPIC
LD_CXX:           g++
LDFLAGS:
LIBFLAGS:         -L.
RLD_FLAG:         -Wl,-rpath -Wl,/usr/lib/octave-3.0.0
BLAS_LIBS:        -llapackgf-3 -lblas-3gf
FFTW_LIBS:        -lfftw3
LIBS:             -lreadline  -lncurses -ldl -lhdf5 -lz -lm
LEXLIB:
LIBGLOB:
SED:              /bin/sed
DEFS:

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   -DHAVE_UMASK=1 -DHAVE_UNAME=1 -DHAVE_UNLINK=1 -DHAVE_USLEEP=1
   -DHAVE_UTIME=1 -DHAVE_VFPRINTF=1 -DHAVE_VSPRINTF=1 -DHAVE_VSNPRINTF=1
   -DHAVE_WAITPID=1 -DHAVE_STRFTIME=1 -DHAVE_LIBDL=1 -DHAVE_DLOPEN=1
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   -DHAVE_TIMES=1 -DYYTEXT_POINTER=1 -DGNUPLOT_BINARY="gnuplot"

User-preferences (please do not edit this section):
--------------------------------------------------

   EDITOR = emacs
   EXEC_PATH =  
/usr/lib/octave/3.0.0/site/exec/x86_64-pc-linux-gnu:/usr/lib/octave/api-v32/site/exec/x86_64-pc-linux-gnu:/usr/lib/octave/site/exec/x86_64-pc-linux-gnu:/usr/lib/octave/3.0.0/exec/x86_64-pc-linux-gnu:/usr/bin:/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin:/usr/games
   IMAGE_PATH = .:/usr/share/octave/3.0.0/imagelib
   PAGER = pager
   PS1 = \s:\#>
   PS2 = >
   PS4 = +
   beep_on_error = 0
   completion_append_char =
   crash_dumps_octave_core = 1
   echo_executing_commands = 0
   fixed_point_format = 0
   gnuplot_binary = gnuplot
   gnuplot_command_end =

   gnuplot_command_plot = pl
   gnuplot_command_replot = rep
   gnuplot_command_splot = sp
   gnuplot_command_title = t
   gnuplot_command_using = u
   gnuplot_command_with = w
   history_file = /home/nasko/.octave_hist
   history_size = 1024
   ignore_function_time_stamp = system
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[John W. Eaton]

On 11-Jun-2008, Atanas Atanasov wrote:

| Bug report for Octave 3.0.0 configured for x86_64-pc-linux-gnu
|
| Description:
| -----------
|
| The functions rat and rats should handle the special case of zero  
| input, which it seems currently they do not do. As a result the user  
| recieves a 'warning: division by zero' and wrong output.
|
| Repeat-By:
| ---------
|
| rat(0)
| [p,q] = rat(0)
| rats(0)
|
| Fix:
| ---
|
| It is possible to check whether the input is zero before calling  
| rat/rats but this is tedious. The check should be incorporated in the  
| beginning of rat.m.

Please try the following patch.

jwe



# HG changeset patch
# User John W. Eaton <jwe@...>
# Date 1213208466 14400
# Node ID f74669a09debfac7ff861b211e526ffaf26306dd
# Parent  7609a985a052aa0eddd09b2f5193f85c4def08f1
rat.m: handle arrays and all-integer inputs

diff --git a/scripts/ChangeLog b/scripts/ChangeLog
--- a/scripts/ChangeLog
+++ b/scripts/ChangeLog
@@ -1,3 +1,9 @@
[phone]  John W. Eaton  <jwe@...>
+
+ * general/rat.m: Properly initialize steps when all elements of
+ input array are integers.  Append spaces as necessary when
+ building  character array.
+
 2008-06-05  Jaroslav Hajek <highegg@...>
 
  * plot/__go_draw_axes__.m: Use fprintf for formatted output.
diff --git a/scripts/general/rat.m b/scripts/general/rat.m
--- a/scripts/general/rat.m
+++ b/scripts/general/rat.m
@@ -64,8 +64,13 @@
   ## grab new factors until all continued fractions converge
   while (1)
     ## determine which fractions have not yet converged
-    idx = find (abs(y-n./d) >= tol);
-    if (isempty(idx)) break; endif
+    idx = find(abs (y-n./d) >= tol);
+    if (isempty(idx))
+      if (isempty (steps))
+ steps = NaN .* ones (nsz, 1);
+      endif
+      break;
+    endif
 
     ## grab the next step in the continued fraction
     flip = 1./frac(idx);
@@ -128,6 +133,13 @@
         endif
       endwhile
       s = [s, repmat(")", 1, j-2)];
+      n_nc = columns (n);
+      s_nc = columns (s);
+      if (n_nc > s_nc)
+ s(:,s_nc+1:n_nc) = " "
+      elseif (s_nc > n_nc)
+ n(:,n_nc+1:s_nc) = " ";
+      endif
       n = cat (1, n, s);
     endfor
   endif

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[Atanas Atanasov-5]

I applied the patch but still seem to get the same error. I am
attaching my new rat.m file, and the diff with the old one. It is
quite possible that this is an issue of patching since this is the
first time I perform the operation.

Thank you for your help in advance.

Best,
Atanas Atanasov

Quoting "John W. Eaton" <jwe@...>:

> On 11-Jun-2008, Atanas Atanasov wrote:
>
> | Bug report for Octave 3.0.0 configured for x86_64-pc-linux-gnu
> |
> | Description:
> | -----------
> |
> | The functions rat and rats should handle the special case of zero
> | input, which it seems currently they do not do. As a result the user
> | recieves a 'warning: division by zero' and wrong output.
> |
> | Repeat-By:
> | ---------
> |
> | rat(0)
> | [p,q] = rat(0)
> | rats(0)
> |
> | Fix:
> | ---
> |
> | It is possible to check whether the input is zero before calling
> | rat/rats but this is tedious. The check should be incorporated in the
> | beginning of rat.m.
>
> Please try the following patch.
>
> jwe
>
>
>

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