[Octave-bug-tracker] [bug #46598] unable to get single eps when specifying class

[Carnë Draug]

URL:
  <http://savannah.gnu.org/bugs/?46598>

                 Summary: unable to get single eps when specifying class
                 Project: GNU Octave
            Submitted by: carandraug
            Submitted on: Thu 03 Dec 2015 13:04:40 GMT
                Category: Octave Function
                Severity: 3 - Normal
                Priority: 5 - Normal
              Item Group: Incorrect Result
                  Status: None
             Assigned to: None
         Originator Name: 
        Originator Email: 
             Open/Closed: Open
         Discussion Lock: Any
                 Release: dev
        Operating System: Any

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Details:

The eps function has the following interface:


 -- Built-in Function: eps
 -- Built-in Function: eps (X)
 -- Built-in Function: eps (N, M)
 -- Built-in Function: eps (N, M, K, ...)
 -- Built-in Function: eps (..., CLASS)


However, it is not possible to use "eps (X, CLASS)" because it thinks we are
calling "eps (N, CLASS)"

Example:


octave> eps (5)
ans =    8.8818e-16
octave> eps (5, "double")
ans =

   2.2204e-16   2.2204e-16   2.2204e-16   2.2204e-16   2.2204e-16
   2.2204e-16   2.2204e-16   2.2204e-16   2.2204e-16   2.2204e-16
   2.2204e-16   2.2204e-16   2.2204e-16   2.2204e-16   2.2204e-16
   2.2204e-16   2.2204e-16   2.2204e-16   2.2204e-16   2.2204e-16
   2.2204e-16   2.2204e-16   2.2204e-16   2.2204e-16   2.2204e-16

octave> eps (5, "single")
ans =

   1.1921e-07   1.1921e-07   1.1921e-07   1.1921e-07   1.1921e-07
   1.1921e-07   1.1921e-07   1.1921e-07   1.1921e-07   1.1921e-07
   1.1921e-07   1.1921e-07   1.1921e-07   1.1921e-07   1.1921e-07
   1.1921e-07   1.1921e-07   1.1921e-07   1.1921e-07   1.1921e-07
   1.1921e-07   1.1921e-07   1.1921e-07   1.1921e-07   1.1921e-07


So in order to actually get 'eps (5, "single")', one needs to do


octave> eps (single (5))
ans =    4.7684e-07


I'm not sure if this should be a mistake of the documentation or if we should
change the function to always require the X argument.  Also, the documentation
does not make it obvious that 'eps (CLASS)' is valid (but I can see how the
ellipsis in 'eps (..., CLASS)' includes the just eps()).




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